Rotating machine control device

ABSTRACT

One or more multiphase power converters are connected to a positive electrode and a negative electrode of a power supply via a high potential line and a low potential line, respectively, convert DC power of the power supply into multiphase alternate current power by operations of a plurality of inverter switching elements, and apply a voltage to each of phase windings of a multiphase winding set. A DC rotating machine switch including switches on a high potential side and a low potential side connected in series via a DC motor terminal connected to a second terminal that is an end of the DC rotating machine on an opposite side to a first terminal. The DC rotating machine switch generates a voltage of the DC motor terminal variable by switching. A control unit controls operations of the inverter switching elements and the DC rotating machine switch.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalPatent Application No. PCT/JP2020/039066 filed on Oct. 16, 2020, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Applications No. 2019-199907 filed on Nov. 1, 2019 and No.2020-094449 filed on May 29, 2020. The entire disclosures of all of theabove applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a rotating machine control device.

BACKGROUND

Conventionally, a rotating machine control device that drives amultiphase rotating machine and a direct current (DC) rotating machineby one drive circuit is known.

SUMMARY

According to an aspect of the present disclosure, a rotating machinecontrol device is configured to drive one or more multiphase rotatingmachines including one or more multiphase winding sets and one or moredirect current rotating machines in which a first terminal that is oneend is connected to a phase current path of one or more phases of atleast one of the multiphase winding sets. The device comprises one ormore multiphase power converters, a DC rotating machine switch, and acontrol unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a diagram of an electric power steering (EPS) system to whichan electric control unit (ECU) (rotating machine control device) of eachembodiment is applied;

FIG. 2 is a diagram of a steer-by-wire (SBW) system to which the ECU(rotating machine control device) of each embodiment is applied;

FIG. 3A is a schematic view for explaining a tilt operation;

FIG. 3B is a schematic view for explaining a telescopic operation;

FIG. 4 is a diagram illustrating a connection configuration example of aconnector;

FIG. 5 is a circuit configuration diagram of a first embodiment(three-phase motor×1, DC motor×1);

FIG. 6 is a circuit configuration diagram of a second embodiment(three-phase motor×1, DC motor×3);

FIG. 7 is a circuit configuration diagram of a third embodiment(three-phase motor relay and DC motor relay being present);

FIG. 8 is a circuit configuration diagram of a fourth embodiment(individual power supply relays and individual noise preventionelements);

FIG. 9 is a circuit configuration diagram of a fifth embodiment(individual power supplies);

FIG. 10 is a circuit configuration diagram of a sixth embodiment(individual power supply relays and common negative-direction powersupply relay);

FIG. 11 is a circuit configuration diagram of a seventh embodiment(individual power supply relays and common negative-direction powersupply relay);

FIG. 12 is a circuit configuration diagram of an eighth embodiment(common power supply relays and common noise prevention element);

FIG. 13 is a circuit configuration diagram of a ninth embodiment (commonDC motor relay at the time of energization in a negative direction);

FIG. 14 is a circuit configuration diagram of a tenth embodiment (commonDC motor relay at the time of energization in a positive direction);

FIG. 15 is a control block diagram of a three-phase control unit;

FIG. 16A is a control block diagram of an example of a DC control unit;

FIG. 16B is a control block diagram of another example of the DC controlunit;

FIG. 17 is a flowchart illustrating an overall operation of the ECU;

FIG. 18 is a flowchart of phase current computation processing;

FIG. 19 is a flowchart of phase voltage computation processing (I);

FIG. 20 is a flowchart of phase voltage computation processing (II)<first pattern>;

FIG. 21 is a flowchart of phase voltage computation processing (III);

FIG. 22 is a flowchart of phase voltage computation processing (II)<second pattern>;

FIG. 23 is a flowchart of DC motor terminal voltage computationprocessing <first pattern>;

FIG. 24 is a flowchart of DC motor terminal voltage computationprocessing <second pattern>;

FIG. 25 is a waveform of a phase current flowing through an inverter;

FIG. 26 is a waveform of a phase current that is applied to athree-phase winding set;

FIG. 27A is a waveform of a voltage command in a configuration where VHand VL are constant;

FIG. 27B is a waveform of a controlled voltage command centered aroundVM in the configuration where VH and VL are constant;

FIG. 28A is a waveform of a voltage command after a shift of a neutralpoint voltage at the time of energization in the positive direction inthe configuration where VH and VL are constant;

FIG. 28B is a waveform of a voltage command after the shift of theneutral point voltage at the time of energization in the negativedirection in the configuration where VH and VL are constant;

FIG. 29 is a control block diagram of a three-phase control unit of aconfiguration example in which VH and VL are variable;

FIG. 30A is a waveform of a voltage command in a configuration where VHand VL are variable;

FIG. 30B is a waveform of a controlled voltage command centered aroundVM in the configuration where VH and VL are variable;

FIG. 31A is a waveform of a voltage command after the shift of theneutral point voltage at the time of energization in the positivedirection in the configuration where VH and VL are variable;

FIG. 31B is a waveform of a voltage command after the shift of theneutral point voltage at the time of energization in the negativedirection in the configuration where VH and VL are variable;

FIG. 32 is a flowchart of the first half (third pattern) of phasevoltage computation processing B;

FIG. 33 is a waveform of a voltage command after the shift of theneutral point voltage corresponding to the third pattern;

FIG. 34 is a flowchart illustrating an operation immediately aftervehicle switching;

FIG. 35 is a diagram illustrating a current path in S741 of FIG. 34 inthe configuration of FIG. 6;

FIG. 36 is a flowchart for switching between the drive and stop of theDC motor during the drive of the three-phase motor;

FIG. 37 is a flowchart (Example 1) for fail-safe threshold switching;

FIG. 38 is a flowchart (Example 2) for fail-safe threshold switching;

FIG. 39 is a time chart illustrating Control Example 1 of the drive andstop of the DC motor during the drive of the three-phase motor;

FIG. 40 is a time chart illustrating Control Example 2 of the drive andstop of the DC motor during the drive of the three-phase motor;

FIG. 41 is an axial sectional view of a two-system electromechanicalintegrated motor;

FIG. 42 is a cross-sectional view taken along a line XLII-XLII of FIG.41;

FIG. 43 is a schematic diagram illustrating a configuration of athree-phase double winding rotating machine;

FIG. 44 is a circuit configuration diagram according to an eleventhembodiment (two-system, DC motor×2 (one side));

FIG. 45 is a circuit configuration diagram according to a twelfthembodiment (two-system, DC motor×2 (both sides));

FIG. 46 is a circuit configuration diagram according to a thirteenthembodiment (two-system, DC motor×4 (both sides));

FIG. 47 is a circuit configuration diagram according to a fourteenthembodiment (two-system, DC motor×6 (both sides));

FIG. 48 is a circuit configuration diagram according to a fifteenthembodiment (two-system, individual power supplies); and

FIG. 49 is a circuit configuration diagram of another embodiment.

DETAILED DESCRIPTION

Hereinafter, examples of the present disclosure will be described.

According to an example of the present disclosure, a rotating machinecontrol device drives a multiphase rotating machine and a DC rotatingmachine with one drive circuit. For example, the motor control devicedrives a three-phase alternate current (AC) motor and two DC motors withone three-phase inverter drive circuit. Specifically, this motor controldevice is used as a vehicle steering device and drives an electric powersteering (EPS) three-phase motor, a tilt DC motor, and a telescopic DCmotor.

In the example of the present disclosure, after an ignition key isturned on, the tilt motor and the telescopic motor are operated inparallel to perform a position adjustment operation. When it isdetermined that the position adjustment operation has not beenperformed, the EPS three-phase motor is driven. That is, one of the DCmotor and the three-phase motor is driven, and the DC motor and thethree-phase motor are not assumed to be driven simultaneously. Inaddition, the energization of the DC motor and the three-phase motorcannot be simultaneously controlled, either, in view of the circuitconfiguration.

Further, there are required a switch for interrupting energization of aphase to which the DC motor is connected among phases of the three-phasemotor at the time of driving the DC motor and a switch for interruptingthe energization of the DC motor at the time of driving the three-phasemotor. For example, in a configuration where one DC motor is connectedbetween two phases of the three-phase motor, at least three switches arerequired.

A rotating machine control device according to an example of the presentdisclosure is configured to drive one or more multiphase rotatingmachines including one or more multiphase winding sets and one or moredirect current rotating machines in which a first terminal that is oneend is connected to a phase current path of one or more phases of atleast one of the multiphase winding sets. The device comprises one ormore multiphase power converters, a DC rotating machine switch, and acontrol unit.

The multiphase power converter is connected to a positive electrode anda negative electrode of a power supply via a high potential line and alow potential line, respectively. The multiphase power converterconverts DC power of the power supply into multiphase AC power byoperations of a plurality of inverter switching elements connected in abridge configuration and applies a voltage to each phase winding of themultiphase winding set.

The DC rotating machine switch is made up of switches on a highpotential side and a low potential side connected in series via a DCmotor terminal. The DC motor terminal is connected to a second terminalthat is an end of the DC rotating machine on the opposite side to thefirst terminal. The DC rotating machine switch makes the voltage of theDC motor terminal variable by switching. The control unit controlsoperations of the inverter switching elements and the DC rotatingmachine switch.

Concerning the reference characters of the inverter switching elementand the DC rotating machine switch, for example, “MU1H” and “MU1L” arecollectively referred to as “MU1H/L”.

The control unit of the present disclosure can simultaneously drive theDC rotating machine by controlling the operation of the DC rotatingmachine switch while controlling the operation of the inverter switchingelements to drive the multiphase rotating machine. For example, in aconfiguration where one DC rotating machine is connected to a phasecurrent path of one phase of one three-phase winding set, it issufficient that there be at least two DC rotating machine switches.Hence the number of switches can be reduced.

Adding a supplementary description of the circuit configuration of thepresent disclosure, in the configuration including the plurality ofmultiphase power converters and the plurality of multiphase windingsets, the second terminal of the DC rotating machine is connected onlyto the DC rotating machine switch and is not directly connected to amultiphase winding set different from the multiphase winding set towhich the first terminal is connected. That is, an inverter switchingelement of a multiphase power converter different from the multiphasepower converter to which the DC rotating machine is connected does notalso serve as a DC rotating machine switch for the DC rotating machine.In short, the DC rotating machine switch is provided independently ofthe inverter switching element. With such a configuration, even when theinverter switching element is on, only the energization of the DCrotating machine can be stopped by turning off the DC rotating machineswitch.

The multiphase rotating machine is, for example, a rotating machine forsteering assist torque output of an electric power steering system orfor reaction torque output of a steer-by-wire system.

The DC rotating machine includes a steering-position actuator that makesa steering position variable, specifically, a tilt actuator or atelescopic actuator of a steering column.

Hereinafter, a plurality of embodiments of the rotating machine controldevice will be described with reference to the drawings. The rotatingmachine control device of each embodiment is applied to an electricpower steering system (hereinafter, “EPS system”) or a steer-by-wiresystem (hereinafter, “SBW system”) of a vehicle and functions as anEPS-ECU or an SBW-ECU. In the following embodiments, the EPS-ECU or theSBW-ECU is collectively referred to as an “ECU”. Further, in principle,first to fifteenth embodiments are collectively referred to as “thepresent embodiment”. However, concerning the number of DC motors to bedriven, an embodiment in which three DC motors are mainly driven will bedescribed as “the present embodiment” except for the first embodiment.In each of the plurality of embodiments, substantially the sameconstituent elements are denoted by the same referencecharacters/numerals, and the description thereof is omitted.

[System Configuration]

First, a system configuration to which an ECU as a “rotating machinecontrol device” is applied in the present embodiment will be describedwith reference to FIGS. 1 to 3B. FIG. 1 illustrates an EPS system 901 inwhich a steering mechanism and a turning mechanism are connectedmechanically. FIG. 2 illustrates an SBW system 902 in which the steeringmechanism and the turning mechanism are separated mechanically. In FIGS.1 and 2, only one side of a tire 99 is illustrated, and the illustrationof the tire on the opposite side is omitted.

As illustrated in FIG. 1, the EPS system 901 includes a steering wheel91, a steering shaft 92, an intermediate shaft 95, a rack 97, and thelike. The steering shaft 92 is included in a steering column 93 and hasone end connected to the steering wheel 91 and the other end connectedto the intermediate shaft 95.

The rack 97, which converts rotation into reciprocating motion with arack and pinion mechanism and transmits the reciprocating motion, isprovided at the end of the intermediate shaft 95 on the side opposite tothe steering wheel 91. When the rack 97 reciprocates, the tire 99 isturned via a tie rod 98 and the knuckle arm 985. Universal joints 961,962 are provided in the middle of the intermediate shaft 95. Thereby, adisplacement due to the tilt operation or the telescopic operation ofthe steering column 93 is absorbed.

A torque sensor 94 is provided in the middle of the steering shaft 92and detects a steering torque Ts of a driver on the basis of thetorsional displacement of a torsion bar. In the EPS system, an ECU 10controls the drive of a three-phase motor 800 on the basis of thesteering torque Ts detected by the torque sensor 94 and a vehicle speedV detected by a vehicle speed sensor 14, and outputs a desired steeringassist torque. As thus described, in the EPS system 901, the rotatingmachine for steering assist torque output is used as a “multiphaserotating machine”. Each signal to the ECU 10 is communicated usingController Area Network (CAN), serial communication, or the like, ortransmitted as an analog voltage signal.

In the present embodiment, three DC motors 710, 720, 730 as “DC rotatingmachines” are provided. A steering lock actuator 710 is provided in thevicinity of the steering wheel 91 and locks the steering wheel 91 so asnot to rotate during parking or the like. The ECU 10 instructs thesteering lock actuator 710 to release or re-lock a steering lock on thebasis of an ON/OFF signal of a vehicle switch 11 on the basis of the ECU10. The vehicle switch 11 corresponds to an ignition switch or a pushswitch of an engine vehicle, a hybrid vehicle, or an electric vehicle.

In the present embodiment, a lane keeping flag F from a lane keepingdetermination circuit 15 is input to the ECU 10. When the lane keepingdetermination circuit 15 determines that the vehicle has deviated fromthe lane or is likely to deviate from the lane, the lane keeping flag Fis generated. When the lane keeping flag F is input, the ECU 10 vibratesthe steering wheel 91 to call the driver's attention.

In the present embodiment, for the sake of convenience, the steeringlock actuator 710 also have a function of a steering vibration actuatorthat vibrates the steering wheel 91 to call the driver's attention. Thesteering lock actuator is described in, for example, JP2017-124794A andthe steering vibration actuator is described in, for example,JP2016-30471A.

A tilt actuator 720 and a telescopic actuator 730 are included in a“steering-position actuator” for changing a steering position and areprovided in the steering column 93. When the driver operates a tiltswitch 12 to input an instruction of “up/down” to the ECU 10, the ECU 10instructs the tilt actuator 720 to perform a tilt operation. Then, asillustrated in FIG. 3A, the tilt actuator 720 adjusts a tilt angle tomove the steering wheel 91 up and down. When the vehicle switch 11 isturned on to activate the vehicle, the vehicle moves to a drivingposition stored in advance, and when the vehicle switch 11 is turned offto stop the vehicle, the vehicle moves to a side where the space for thedriver becomes larger.

When the driver operates a telescopic switch 13 to input an instructionof “stretch/shrink” to the ECU 10, the ECU 10 instructs the telescopicactuator 730 to perform a telescopic operation. Then, as illustrated inFIG. 3B, the telescopic actuator 730 adjusts a telescopic length andmoves the steering wheel 91 back and forth. When the vehicle switch 11is turned on to activate the vehicle, the vehicle moves to a drivingposition stored in advance, and when the vehicle switch 11 is turned offto stop the vehicle, the vehicle moves to a side where the space for thedriver becomes larger.

Subsequently, as illustrated in FIG. 2, in the SBW system 902 in whichthe steering mechanism and the turning mechanism are mechanicallyseparated, the intermediate shaft 95 does not exist as compared to theEPS system 901. The steering torque Ts of the driver is electricallytransmitted to a steering motor 890 via the ECU 10. The rotation of thesteering motor 890 is converted into the reciprocating motion of therack 97, and the tire 99 is turned via the tie rod 98 and the knucklearm 985. Although not illustrated in FIG. 2, there is a turning motorECU that drives the steering motor 890 in response to the steering wheelinput of the driver.

In the SBW system 902, the driver cannot directly sense the reactionforce to the steering. Therefore, the ECU 10 controls the drive of thethree-phase motor 800, rotates the steering wheel 91 so as to apply areaction force to steering, and gives the driver an appropriate steeringfeeling. As thus described, in the SBW system 902, the rotating machinefor reaction torque output is used as a “multiphase rotating machine”.

In the SBW system 902 of FIG. 2, the three DC motors as the “DC rotatingmachines”, that is, the steering lock actuator 710, the tilt actuator720, and the telescopic actuator 730, are used similarly to the EPSsystem 901 of FIG. 1. Hereinafter, there is no difference between theEPS system 901 and the SBW system 902 in the description of the controlof the three-phase motor 800 and the DC motors 710, 720, 730 by the ECU10.

The DC motor type actuator used in the present embodiment may be a seatactuator and a steering wheel retraction actuator in addition to thesteering actuators such as the steering lock, tilt, and telescopicactuators. The seat actuator includes an actuator that slides a seat inthe front-rear direction or the height direction or reclines a backrest.

Concerning the configuration of the three-phase motor 800, a unitincluding each of three-phase winding sets 801, 802 and constituentelements such as an inverter corresponding to the winding set isreferred to as a “system”. Each of the first to tenth embodiments has aone-system configuration, and each of the eleventh to fifteenthembodiments has a two-system configuration where each constituentelement is redundantly provided. Since the one-system motor structure isa general well-known technique, the description thereof is omitted, andthe two-system motor structure will be described later. At the end ofeach of the reference characters and symbols of the two-systemconfiguration, “1” is added for a configuration of a first system, and“2” is added for a configuration of a second system. In the one-systemconfiguration, the reference characters and symbols of the first systemin the two-system configuration are used.

Next, a connection configuration of devices will be described withreference to FIG. 4. The three-phase motor 800 of the present embodimentis configured as an “electromechanical integrated motor” in which theECU 10 is integrally configured on one side in the axial direction. Onthe other hand, each of the three DC motors 710, 720, 730 is connectedto the ECU 10 via a connector. That is, while the connection between thethree-phase motor 800 and the ECU 10 is assumed to be fixed, each of theDC motors 710, 720, 730 and the ECU 10 may be configured to beconnectable as an option corresponding to the needs, a connector on theECU 10 side need not be mounted in accordance with the option, and acircuit board may be common.

FIG. 4 illustrates an example of a connector connection configuration.In this configuration example, a power system connector 591, a signalsystem connector 592, and a torque sensor connector 593 are providedseparately. To the power system connector 591, a power supply line (PIG)from a DC power supply and a ground line are connected. To the signalsystem connector 592, the wiring of each of the DC motors 710, 720, 730is connected in addition to a control power supply line (IG) and a CANcommunication line.

Although motor lines (M+, M−) of each of the DC motors 710, 720, 730 arepower systems, the motor lines can be included in the signal systemconnector 592 and connected because of having a motor current smallerthan that of the three-phase motor 800. When the current of each of theDC motors 710, 720, 730 is large, another connector may be used, or aconnector common to the power system connector 591 of the power supplyline (PIG) from the DC power supply and the ground line may be used.

Two motor lines (M+, M−) are connected to the steering lock actuator710. Five lines, which are motor lines (M+, M−), a position sensor powersupply line, a position sensor signal line, and a ground line, areconnected to each of the tilt actuator 720 and the telescopic actuator730. It is also possible to make a configuration in which the positionsensor is not used by determining that a predetermined position isreached based on torque or current and time, or applying a constantcurrent or voltage in accordance with ON/OFF of the tilt switch 12 andthe telescopic switch 13. FIG. 4 illustrates an example in which asignal is received from each of the tilt switch 12 and the telescopicswitch 13 by CAN communication, but in a case where an analog voltagesignal is received, the lines can be included in the signal systemconnector 592 and connected. The connector may be divided for each ofthe DC motors 710, 720, 730. A power supply line, a signal line, and aground line of the torque sensor 94 are collectively connected to thetorque sensor connector 593.

[Circuit Configuration in which One-System Three-Phase Motor is Driven]

Next, with reference to circuit configuration diagrams of FIGS. 5 to 14,a configuration example of the ECU 10 to drive the one-systemthree-phase motor 800 will be described as first to tenth embodiments.For the reference character of the ECU, “10” is used in all theembodiments regardless of the difference in configuration. Among theelements illustrated in each drawing, a portion except for thethree-phase winding set 801 of the three-phase motor 800 and the DCmotors 710, 720, 730 is the ECU 10.

First and second embodiments are basic configurations of the presentdisclosure. In particular, the first embodiment aims to disclose aminimum configuration in which only one three-phase motor 800 and one DCmotor 710 are to be driven, and does not directly correspond to thesystem configuration in FIGS. 1 to 3B. The second embodiment in whichone three-phase motor 800 and three DC motors 710, 720, 730 are to bedriven directly corresponds to the system configuration in FIGS. 1 to3B. In the third and subsequent embodiments, an applied configuration isadded based on the configuration of the second embodiment.

First Embodiment

FIG. 5 illustrates an overall configuration of the ECU 10 according tothe first embodiment. The three-phase winding set 801 of the three-phasemotor 800 is configured by connecting U1-phase, V1-phase, and W1-phasewindings 811, 812, 813 at a neutral point N1. The voltage at the neutralpoint N1 is defined as a neutral point voltage Vn1. The referencecharacter “800” of the three-phase motor and the reference characters“811, 812, 813” of the three-phase windings are illustrated only in FIG.5 and are not illustrated in FIGS. 6 to 14. As illustrated in FIG. 43related to the description of the two-system configuration to bedescribed later, a counter-electromotive voltage proportional to theproduct of a rotational speed and a sin value of a phase is generated ineach phase of the three-phase motor 800. An electrical angle θ of thethree-phase motor 800 is detected by a rotational angle sensor.

The ECU 10 includes one inverter 601 as a “multiphase power converter”,two DC motor switches MU1H, MU1L as “DC rotating machine switches”, anda control unit 30. The inverter 601 is connected to a positive electrodeof a power supply Bt1 via a high potential line BH1 and is connected toa negative electrode of the power supply Bt1 via a low potential lineBL1. The power supply Bt1 is, for example, a battery having a referencevoltage of 12 [V]. A DC voltage input from the power supply Bt1 to theinverter 601 is referred to as an “input voltage Vr1”. On the powersupply Bt1 side of the inverter 601, a capacitor C1 is provided betweenthe high potential line BH1 and the low potential line BL1.

The inverter 601 converts DC power of the power supply Bt1 intothree-phase AC power by operations of a plurality of inverter switchingelements IU1H, IU1L, IV1H, IV1L, IW1H, IW1L on the high potential sideand the low potential side, which are connected in a bridgeconfiguration. The inverter 601 then applies a voltage to each of thephase windings 811, 812, 813 of the three-phase winding set 801.

Specifically, the inverter switching elements IU1H, IV1H, IW1H are upperarm elements provided on the high potential sides of the U1 phase, theV1 phase, and the W1 phase, respectively, and the inverter switchingelements IU1L, IV1L, IW1L are lower arm elements provided on the lowpotential sides of the U1 phase, the V1 phase, and the W1 phase,respectively. Hereinafter, the reference characters of the upper armelements and the lower arm elements of the same phases are collectivelyreferred to as “IU1H/L, IV1H/L, IW1H/L”. Each of switches used in thepresent embodiment, including the inverter switching elements IU1H/L,IV1H/L, IW1H/L, is a MOSFET, for example. Each of the switches may be afield-effect transistor in addition to the MOSFET, an insulated-gatebipolar transistor (IGBT), and the like.

Current sensors SAU1, SAV1, SAW1 that detect phase currents Iu1, Iv1,Iw1 flowing through the respective phases of the inverter 601 areinstalled between the lower arm elements IU1L, IV1L, IW1L of therespective phases and the low potential line BL1. The current sensorsSAU1, SAV1, SAW1 are formed of, for example, shunt resistors. Withrespect to the phase currents Iu1, Iv1, Iw1 flowing through the inverter601, phase currents that are applied through the three-phase winding set801 are referred to as Iu1#, Iv1#, and Iw1#. The relationship betweenboth phase currents will be described later.

A DC motor switch as a “DC rotating machine switch” is made up of aswitch MU1H on a high potential side and a switch MU1L on a lowpotential side, which are connected in series via a DC motor terminalM1. Similarly to the inverter switching elements, the referencecharacters of the DC motor switches on the high potential side and thelow potential side are collectively referred to as “MU1H/L”. The DCmotor switch MU1H/L except for that of the fifth embodiment is providedbetween the high potential line BH1 and the low potential line BL1 inparallel with the inverter 601 with respect to the power supply Bt1common to the inverter 601.

A first terminal T1, which is one end of the DC motor 710, is connectedto a branch point Ju of the U1-phase current path of the three-phasewinding set 801. A second terminal T2, which is an end of the DC motor710 on the opposite side to the first terminal T1, is connected to theDC motor terminal M1 of the DC motor switch MU1H/L. Therefore, the DCmotor switch MU1H/L is connected to the U1 phase of the three-phasewinding set 801 via the DC motor 710. “U” in the reference character“MU1H/L” of the DC motor switch means the U1 phase, and “1” means thefirst DC motor 710.

In the DC motor 710, the direction of the current flowing from the firstterminal T1 to the second terminal T2 is defined as a positivedirection, and the direction of the current flowing from the secondterminal T2 to the first terminal T1 is defined as a negative direction.A voltage Vx is applied between the first terminal T1 and the secondterminal T2. The DC motor 710 rotates forward when energized in thepositive direction, and rotates backward when energized in the negativedirection. At the time of energization of the DC motor 710, acounter-electromotive voltage E1 proportional to a rotational speed ω1is generated. That is, when a proportionality constant is E, thecounter-electromotive voltage E1 is expressed by a formula “E1=−Eω1”.The reference characters “T1, T2” of the first terminal and the secondterminal are illustrated only in FIG. 5 and are not illustrated in FIG.6 and subsequent drawings.

The DC motor switch MU1H/L performs switching by duty control or thelike to make a voltage Vm1 of the DC motor terminal M1 variable. Here,since the current that is applied to the DC motor 710 is smaller thanthe phase current flowing through the three-phase motor 800, a switchhaving a smaller current capacity than the inverter switching elementsIU1H/L, IV1H/L, IW1H/L is used as the DC motor switch MU1H/L.

Adding a supplementary description of the circuit configuration of thepresent embodiment, in the configuration including the plurality ofinverters and the plurality of three-phase winding sets, the secondterminal of the DC motor is connected only to the DC motor switch and isnot directly connected to a three-phase winding set different from thethree-phase winding set to which the first terminal is connected. Thatis, an inverter switching element of an inverter different from theinverter to which the DC motor is connected does not also serve as a DCmotor switch for the DC motor. In short, the DC motor switch is providedindependently of the inverter switching element. With such aconfiguration, even when the inverter switching element is on, only theenergization of the DC motor can be stopped by turning off the DC motorswitch.

The control unit 30 acquires the electrical angle θ of the three-phasemotor 800 and the three-phase currents Iu1, Iv1, Iw1. The control unit30 controls the operations of the inverter switching elements IU1H/L,IV1H/L, IW1H/L and the DC motor switch MU1H/L on the basis of dq-axiscurrent command values Id*, Iq* for the three-phase motor 800 and a DCcurrent command value I1* for the DC motor 710. Details of the controlconfiguration of the control unit 30 will be described later withreference to FIGS. 15 to 16B. In circuit configuration diagrams of FIG.6 and subsequent drawings, illustration of the control unit 30 and inputsignals is omitted.

Second Embodiment

In the second embodiment illustrated in FIG. 6, the three DC motors 710,720, 730 are connected to the U1 phase, the V1 phase, and the W1 phaseof the three-phase winding set 801. Here, the names of the DC motorswill be described in accordance with the system configurations of FIGS.1 to 3B. The first terminal of the steering lock actuator 710 isconnected to the branch point Ju of the U1-phase current path of thethree-phase winding set 801. The first terminal of the tilt actuator 720is connected to a branch point Jv of the V1 phase current path of thethree-phase winding set 801. The first terminal of the telescopicactuator 730 is connected to a branch point Jw of the W1-phase currentpath of the three-phase winding set 801.

In the second embodiment, three sets of DC motor switches MU1H/L,MV2H/L, MW3H/L are provided in accordance with the three DC motors 710,720, 730. The second terminal of the steering lock actuator 710 isconnected to the DC motor terminal M1 of the DC motor switch MU1H/L. Thesecond terminal of the tilt actuator 720 is connected to a DC motorterminal M2 of the DC motor switch MV2H/L. The second terminal of thetelescopic actuator 730 is connected to a DC motor terminal M3 of the DCmotor switch MW3H/L.

“V” in the reference character “MV2H/L” of the DC motor switch means theV1 phase, and “2” means the second DC motor 720. “W” in the referencecharacter “MW3H/L” means the W1 phase, and “3” means the third DC motor730. The DC motor switches MU1H/L, MV2H/L, MW3H/L perform switching byduty control or the like to make voltages Vm1, Vm2, Vm3 of the DC motorterminals M1, M2, M3 variable.

Hereinafter, one DC motor selected as an energization target among oneor more DC motors is referred to as a “specific DC motor”. The ECU 10can energize the “specific DC motor” simultaneously with energizing thethree-phase motor 800. The DC current that is applied to the DC motor710, 720, or 730 selected as the specific DC motor is referred to as I1,I2, or I3. The DC motors 710, 720, 730 rotate forward or backward inaccordance with the positive or negative of the DC currents I1, I2, I3.At the time of energization of the specific DC motor, acounter-electromotive voltage proportional to the rotational speed isgenerated. The counter-electromotive voltages generated in the DC motors710, 720, 730 are referred to as E1, E2, and E3, respectively.

Hereinafter, in the second to fifteenth embodiments, a plurality of, twoto six, DC motors are connected to the three-phase winding sets 801,802. In the present embodiment, the number of DC motors connected to onephase of each of the three-phase winding sets 801, 802 is one or less.That is, three or less DC motors can be connected to the three-phasewinding set, and N or less DC motors can be connected to the N-phasewinding set. In a configuration where a plurality of DC motors areconnected, (A) a plurality of DC motors are connected to a plurality ofphases of one three-phase winding set 801, or (B) a plurality of DCmotors in total are connected to one or more phases of each of theplurality of three-phase winding sets 801, 802. Among the second tofifteenth embodiments, embodiments except for the twelfth embodimentcorrespond to the example of (A), and the twelfth to fifteenthembodiments correspond to the example of (B).

Third Embodiment

In the third embodiment illustrated in FIG. 7, as compared to the secondembodiment, three-phase motor relays MmU1, MmV1, MmW1 and DC motorrelays MU1 r, MU1R, MV2 r, MV2R, MW3 r, MW3R are further included. Eachmotor relay is formed of a semiconductor switching element, a mechanicalrelay, or the like. In each of the embodiments illustrated in FIG. 7 andsubsequent drawings, each motor relay is formed of ametal-oxide-semiconductor field-effect transistor (MOSFET) having aparasitic diode.

The three-phase motor relays MmU1, MmV1, MmW1 are provided in therespective phase current paths between the inverter 601 and thethree-phase winding set 801. Specifically, in the U1, V1, and W1 phasesto which the DC motors 710, 720, 730 are connected, the three-phasemotor relays MmU1, MmV1, MmW1 are provided closer to the three-phasemotor 800 than the branch points Ju, Jv, Jw to the DC motors 710, 720,730 in the respective phase current paths.

For example, when energizing the three-phase motor 800, the control unit30 turns on the three-phase motor relays MmU1, MmV1, MmW1. On the otherhand, when not energizing the three-phase motor 800, the control unit 30turns off the three-phase motor relays MmU1, MmV1, MmW1. When being off,the three-phase motor relays MmU1, MmV1, MmW1 can interrupt a currentfrom the three-phase motor 800 to the inverter 601, that is, a currentcaused by the counter-electromotive force. In addition, for example,even when the inverter switching element IU1H has a short-circuitfailure, the current flowing from the three-phase motor 800 to theinverter 601 can be interrupted by the counter-electromotive voltage.

The DC motor relays MU1 r, MU1R, MV2 r, MV2R, MW3 r, MW3R are providedcloser to the DC motors 710, 720, 730 than the branch points Ju, Jv, Jwof the respective phase current paths. Here, the DC motor relays MU1 r,MV2 r, MW3 r that interrupt the current in the positive direction whenturned off are referred to as “positive-direction DC motor relays”, andthe DC motor relays MU1R, MV2R, MW3R that interrupt the current in thenegative direction when turned off are referred to as“negative-direction DC motor relays”.

In the example of FIG. 7, the positive-direction DC motor relays MU1 r,MV2 r, MW3 r are connected in series on the sides of the branch pointsJu, Jv, Jw, and the negative-direction DC motor relays MU1R, MV2R, MW3Rare connected in series on the sides of the DC motors 710, 720, 730 suchthat the source terminals of the MOSFETs are adjacent to each other. Thereference characters of the positive-direction motor relay MU1 r and thenegative-direction motor relay MU1R connected in series to the DC motor710 are collectively referred to as “MU1 r/R”. Similarly, the referencecharacters of the motor relays in both the positive and negativedirections connected in series to the DC motors 720, 730 are referred toas “MV2 r/R” and “MW3 r/R”, respectively.

In the third embodiment, it is possible to switch between energizationand interruption of the DC motors 710, 720, 730 by using the DC motorrelays MU1 r/R, MV2 r/R, MW3 r/R in addition to the DC motor switchesMU1H/L, MV2H/L, MW3H/L. For example, even when the DC motor switch MU1Hon the high potential side of the DC motor 710 has a short-circuitfailure, the DC motor relay MU1 r/R can be turned off to safely stop theDC motor 710.

(Power Supply Relay and Noise Prevention Element)

The ECU 10 according to each of the following fourth to tenthembodiments further includes a power supply relay and a noise preventionelement. The power supply relay is formed of a semiconductor switchingelement, a mechanical relay, or the like, and can interrupt energizationfrom the power supply Bt1 to a load when the power supply relay isturned off. For example, in a case where the power supply relay isformed of a MOSFET, a current flows in one direction even when the powersupply relay is off in accordance with the direction of the parasiticdiode, and hence it is necessary to distinguish in which direction thecurrent can be interrupted.

In the present specification, a direction in which a current flows whenthe electrode of the power supply Bt1 is connected in a normal directionis referred to as a positive direction, and a power supply relay thatinterrupts a current in the positive direction when turned off isreferred to as a “power supply relay in the positive direction”. Adirection in which a current flows when the electrode of the powersupply Bt1 is connected in a direction opposite to the normal directionis referred to as a negative direction, and a power supply relay thatinterrupts a current in the negative direction when turned off isreferred to as a “negative-direction power supply relay”. The powersupply relay in the negative direction is generally referred to as a“reverse connection prevention relay” or a “reverse connectionprotection relay”, but in the present specification, the power supplyrelay is referred to as a “negative-direction power supply relay” inorder to unify terms with the DC motor relay in the positive andnegative directions.

The reference character of the positive-direction power supply relayprovided in the current path from the power supply Bt1 to the inverter601 is referred to as “P1 r”, and the reference character of thenegative-direction power supply relay is referred to as “P1R”. Ingeneral, the positive-direction power supply relay P1 r is connected inseries on the power supply Bt1 side, and the negative-direction powersupply relay P1R is connected in series on the inverter 601 side. Thereference characters of the positive-direction power supply relay P1 rand the negative-direction power supply relay P1R connected in seriesare collectively referred to as “P1 r/R”. In the configuration where theother power supply relays are provided in the current paths from thepower supply Bt1 to the DC motor switches MU1H/L, MV2H/L, MW3H/L, thereference characters of the other positive-direction power supply relayand the other negative-direction power supply relay are referred to as“Pdr”, “PdR”, respectively, and are collectively referred to as “Pdr/R”.

The noise prevention element is a coil and a capacitor that function asa noise filter. The reference characters of the noise preventionelements provided in the input units of the inverter 601 are referred toas “L1” and “C1”. In a configuration where the input units of the DCmotor switches MU1H/L, MV2H/L, MW3H/L are provided with other noiseprevention elements, the reference characters of the other noiseprevention elements are referred to as “Ld” and “Cd”.

Fourth Embodiment

In the fourth embodiment illustrated in FIG. 8, a power supply relay inboth positive and negative directions, and a coil and a capacitor as anoise prevention element are individually provided for the inverter 601and the DC motor switches MU1H/L, MV2H/L, MW3H/L. That is, the powersupply relay P1 r/R, the coil L1, and the capacitor C1 are providedbetween the power supply Bt1 and the inverter 601. The power supplyrelay Pdr/R, the coil Ld, and the capacitor Cd are provided between thepower supply Bt1 and the DC motor switches MU1H/L, MV2H/L, MW3H/L.

The power supply relay Pdr/R on the DC motor switch side interruptsenergization from the power supply Bt1 to the DC motors 710, 720, 730,and the power supply relay P1 r/R on the inverter side interruptsenergization from the power supply Bt1 to the three-phase motor 800.Here, since the current that is applied to each of the DC motors 710,720, 730 is smaller than the phase current flowing through thethree-phase motor 800, a switch having a current capacity smaller thanthat of the power supply relay P1 r/R on the inverter side is used asthe power supply relay Pdr/R on the DC motor switch side.

Fifth Embodiment

The fifth embodiment illustrated in FIG. 9 is different from the fourthembodiment in the connection configuration of the power supply. In thefifth embodiment, the inverter 601 and the DC motor switches MU1H/L,MV2H/L, MW3H/L are connected to the individual power supplies Bt1, Btd.The DC voltage input from the power supply Btd to each of the DC motorswitches MU1H/L, MV2H/L, MW3H/L is referred to as an “input voltageVrd”. The individual power supplies Bt1, Btd may be branched from anoriginal common power supply via another wiring or fuse. A broken linebetween the positive electrode of the power supply Bt1 and the positiveelectrode of the power supply Btd indicated by a mark (*) in FIG. 9indicates that the two power supplies Bt1, Btd are connected to theoriginal common power supply. With this configuration, the influence ofpower supply noise, power supply voltage fluctuation, and the like canbe prevented or isolated between the power supplies.

Sixth and Seventh Embodiments

In the sixth and seventh embodiments illustrated in FIGS. 10 and 11,similarly to the fourth embodiment, the positive-direction power supplyrelay and the noise prevention element are individually provided for theinverter 601 and the DC motor switches MU1H/L, MV2H/L, MW3H/L. However,a negative-direction power supply relay PR1 is provided in common withthe inverter 601 and the DC motor switches MU1H/L, MV2H/L, MW3H/L. Thecommon negative-direction power supply relay P1R is provided on thenegative electrode side of the power supply Bt1 in the sixth embodimentand is provided on the positive electrode side of the power supply Bt1in the seventh embodiment. As thus described, the positive-directionpower supply relays P1 r, Pdr and the negative-direction power supplyrelay P1R may have different arrangement configurations.

Eighth Embodiment

In an eighth embodiment illustrated in FIG. 12, as compared to thefourth embodiment, the power supply relay P1 r/R in both positive andnegative directions, and the coil L1 and the capacitor C1 as the noiseprevention elements are provided in common for the inverter 601 and theDC motor switches MU1H/L, MV2H/L, MW3H/L. With this configuration, thenumber of elements can be reduced.

Ninth Embodiment

In the ninth embodiment illustrated in FIG. 13, as compared to theeighth embodiment, a common negative-direction relay McomR is providedon the high potential line BH1 instead of eliminating thenegative-direction DC motor relays MU1R, MV2R, MW3R. The commonnegative-direction relay McomR can interrupt the current flowing in thenegative direction of the DC motors 710, 720, 730 at the time ofturning-off. With this configuration, the number of negative-directionrelays can be reduced.

Tenth Embodiment

In the tenth embodiment illustrated in FIG. 14, as compared to theeighth embodiment, a common positive-direction relay Mcomr is providedon the low potential line BL1 instead of the positive-direction DC motorrelays MU1 r, MV2 r, MW3 r. The common positive-direction relay Mcomrcan interrupt the current flowing in the positive direction of each ofthe DC motors 710, 720, 730 at the time of turning-off. With thisconfiguration, the number of positive-direction relays can be reduced.

[Control Configuration of ECU]

Next, the control configuration of the ECU 10 will be described. In thedescription of this portion, the third to eighth embodiments of theabove embodiments are mainly assumed in which the three DC motors 710,720, 730 are driven, and the three-phase motor relays MmU1, MmV1, MmW1and the DC motor relays MU1 r/R, MV2 r/R, MW3 r/R are provided.

A detailed configuration of the control unit 30 will be described withreference to FIGS. 15 to 16B. The control unit 30 is made up of amicrocomputer, a drive circuit, and the like and includes a centralprocessing unit (CPU), a read-only memory (ROM), a random-access memory(RAM), an input/output (I/O) (not illustrated), and a bus lineconnecting these constituent elements, and the like. The control unit 30executes control by software processing performed by the CPU executing aprogram stored in advance in a tangible memory device (i.e., a readablenon-transitory tangible recording medium) such as a ROM or hardwareprocessing performed by a dedicated electronic circuit.

The control unit 30 controls the operations of the inverter switchingelements IU1H/L, IV1H/L, IW1H/L and the DC motor switches MU1H/L,MV2H/L, MW3H/L and the opening and closing of the DC motor relays MU1r/R, MV2 r/R, MW3 r/R and the three-phase motor relays MmU1, MmV1, MmW1.

The control unit 30 includes a three-phase control unit 301 and a DCcontrol unit 40. As illustrated in FIG. 15, the three-phase control unit301 includes a current limit value computation unit 311, a temperatureestimation computation unit 321, a phase current computation unit 331, athree-phase to two-phase conversion unit 341, a current deviationcomputing device 351, a controller 361, a two-phase to three-phaseconversion unit 371, a phase voltage computation unit 381, and a DCmotor terminal voltage computation unit 383.

The three-phase control unit 301 receives the dq-axis current commandvalues Id*, Iq* computed on the basis of the steering torque Ts detectedby the torque sensor 94. The current limit value computation unit 311computes dq-axis current command values Id1**, Iq1** after currentlimitation on the basis of dq-axis current command values Id*, Iq* andan estimated temperature H_est1. In order to prevent the temperatures ofthe inverter switching elements IU1H/L, IV1H/L, IW1H/L and the like fromexceeding a heat-resistant temperature due to a temperature rise, acurrent limit value is set lower as the estimated temperature H_est1 ishigher.

On the basis of the phase currents Iu1, Iv1, Iw1, the temperatureestimation computation unit 321 computes a rising temperature caused byenergization from the product (I²R) of a current square value andresistance and estimates the substrate temperature of the inverter 601.Generally, in the three-phase motor control, the rising temperature iscomputed on the basis of a dq-axis current after coordinate conversion.However, in the present embodiment, with the specific DC motor beingalso energized, the rising temperature is computed on the basis of acurrent corresponding to a portion where the temperature is estimated.For example, the electric circuit performs estimation based on the phasecurrents Iu1, Iv1, Iw1, and the coil performs estimation based on thepower supply current computed on the basis of the phase currents Iu1,Iv1, Iw1. A phase current before the current to be applied is subtractedneeds to be used as the temperature of the motor, and hence aconfiguration different from general three-phase motor control isadopted.

On the basis of the phase currents Iu1, Iv1, Iw1 flowing through theinverter 601, the phase current computation unit 331 computes the motorphase currents Iu1#, Iv1#, Iw1# that are applied to the three-phasewinding set 801 and the DC currents I1, I2, or I3 that is applied to thespecific DC motor. The motor phase currents Iu1#, Iv1#, Iw1# are outputto the three-phase to two-phase conversion unit 341. The DC current I1,I2, or I3 computed by the phase current computation unit 331 is outputto the DC control unit 40. Details of the phase current computation willbe described later with reference to FIG. 18 and the like.

The three-phase to two-phase conversion unit 341 performs coordinateconversion on the motor phase currents Iu1#, Iv1#, Iw1# by using theelectrical angle θ and feeds back dq-axis currents Id1, Iq1 to thecurrent deviation computing device 351. The current deviation computingdevice 351 subtracts the dq-axis currents Id1, Iq1 from the dq-axiscurrent command values Id1**, Iq1** to compute current deviations ΔId1,ΔIq1. The controller 361 computes dq-axis voltage commands Vd1, Vq1 byproportional-integral (PI) control or the like so as to bring thecurrent deviations ΔId1, ΔIq1 close to 0. The two-phase to three-phaseconversion unit 371 performs coordinate conversion on dq-axis voltagecommands Vd1, Vq1 by using the electrical angle 8 to compute three-phasevoltage commands Vu1, Vv1, Vw1.

The phase voltage computation unit 381 computes controlled phasevoltages Vu1#, Vv1#, Vw1# on the basis of the three-phase voltagecommands Vu1, Vv1, Vw1 and a DC motor applied voltage Vx input from theDC control unit 40. The DC motor terminal voltage computation unit 383computes the DC motor terminal voltages Vm1, Vm2, Vm3 on the basis ofthe controlled phase voltages Vu1#, Vv1#, Vw1# and the DC motor appliedvoltage Vx. Details of the phase voltage computation and the DC motorterminal voltage computation will be described later with reference toFIGS. 19 to 24 and the like.

As illustrated in FIG. 16A, the DC control unit 40 includes a currentdeviation computing device 45 and a controller 46. The current deviationcomputing device 45 subtracts the DC current I1, I2, or I3 computed bythe phase current computation unit 331 from the DC current command valueI1*, I2*, or I3* for the specific DC motor to compute a currentdeviation ΔI1, ΔI2, or ΔI3. The controller 46 computes the voltage Vxapplied to the DC motor by PI control or the like such that the currentdeviation ΔI1, ΔI2, or ΔI3 approaches 0, and outputs the voltage Vx tothe phase voltage computation unit 381 of the three-phase control unit301. The applied voltage Vx may be set independently for each DC motor,but for convenience, the symbol “Vx” is used in common for all DCmotors. As illustrated in FIG. 16B, the voltage Vx that is applied tothe DC motor may be computed by map computation or the like from the DCcurrent command value I1*, I2*, or I3* without computating a currentdeviation.

Next, the overall operation of the ECU 10 will be described withreference to a flowchart of FIG. 17. In the following description of theflowchart, the symbol “S” indicates a step. The substantially same stepas that in the previous flowchart is denoted by the same step number,and the description thereof is omitted. The routine of FIG. 17 starts byturning on the vehicle switch 11. S01 will be described in second andsubsequent rounds of the routine. In a first round after the start, thatis, in a first routine, the determination is NO in S01, and theprocessing proceeds to S11.

In the first routine, the determination is YES in S11, and theprocessing proceeds to S12. In S12, the control unit 30 drives the tiltactuator 720 and the telescopic actuator 730 to move the tilt and thetelescopic to stored positions. Further, the control unit 30 drives thesteering lock actuator 710 in S13 to release the steering lock. In thesecond and subsequent rounds of the routine, the determination is NO inS11, and S12 and S13 are skipped.

In S14, the control unit 30 turns on the three-phase motor relays MmU1,MmV1, MmW1 and the DC motor relays MU1 r/R, MV2 r/R, MW3 r/R to make thethree-phase motor 800 or the DC motors 710, 720, 730 drivable inresponse to a torque request.

Steps S15 to S23 are steps of selecting one specific DC motor among thethree DC motors 710, 720, 730. In S15, the control unit 30 determineswhether an absolute value |Ts| of the steering torque is less than atorque threshold Ts_th (e.g., 5 [Nm]). Here, the steering torque Ts isdefined, for example, such that the left rotation direction is positiveand the right rotation direction is negative in accordance with thedirection of the torque applied to the steering wheel 91. Since there isbasically no difference in characteristics depending on the rotationdirection, the absolute value |Ts| of the steering torque includes thesteering torque Ts in each direction and is compared with the torquethreshold Ts_th.

When the absolute value |Ts| of the steering torque is equal to orlarger than the torque threshold Ts_th, that is, during steering by thedriver, the determination is NO in S15. Since it is preferable not tomove the tilt or the telescopic during steering, the DC motors 710, 720,730 are not energized, and the processing returns to before 501. On theother hand, when the absolute value |Ts| of the steering torque is lessthan the torque threshold Ts_th, that is, when the driver is notsubstantially steering, the determination is YES in S15, and theprocessing proceeds to S16.

In S16, it is determined whether or not the lane keeping flag F has beeninput from the lane keeping determination circuit 15. When thedetermination is YES in S16, the control unit 30 drives the steeringlock actuator 710 that also functions as the steering vibration actuatorin S21. In this case, the steering lock actuator 710 vibrates thesteering wheel 91 to call the driver's attention.

When the determination is NO in S16, it is determined in S17 whether thevehicle speed V is less than a vehicle speed threshold V_th (e.g., 30[km/h]). During high-speed traveling in which the vehicle speed V isequal to or higher than the vehicle speed threshold V_th and thedetermination is NO in S17, it is preferable not to move the tilt or thetelescopic. Thus, the tilt actuator 720 and the telescopic actuator 730are not energized, and the processing returns to before S01. On theother hand, during low-speed traveling in which the vehicle speed V isless than the vehicle speed threshold V_th and the determination is YESin S17, the energization of the tilt actuator 720 and the telescopicactuator 730 is permitted.

When there is a tilt input from the tilt switch 12, the determination isYES in S18, and the control unit 30 drives the tilt actuator 720 in S22.When the determination is NO in S18 and there is a telescopic input fromthe telescopic switch 13, the determination is YES in S19, and thecontrol unit 30 drives the telescopic actuator 730 in S23.

After the respective DC motors 710, 720, 730 are driven in S21, S22, andS23, or when the determination is NO in S15 or S17, the processingreturns to before S01, and it is determined whether or not the vehicleswitch 11 has been turned off. When the vehicle switch 11 remains on andthe determination is NO in S01, the routine from S11 is repeated. Whenthe vehicle switch 11 is turned off and the determination is YES in S01,the control unit 30 turns off the three-phase motor relays MmU1, MmV1,MmW1 and the DC motor relays MU1 r/R, MV2 r/R, MW3 r/R in S02.Thereafter, in S03, the control unit 30 drives the steering lockactuator 710 to lock the steering and ends the processing.

Next, phase current computation processing by the phase currentcomputation unit 331 will be described with reference to a flowchart ofFIG. 18 and current waveform diagrams of FIGS. 25 and 26 The controlunit 30 applies Kirchhoff's law to the current flowing from the inverter601 into the three-phase winding set 801 and computes the motor phasecurrents Iu1#, Iv1#, Iw1# that are applied to the three-phase motor 800,and the currents I1, I2, I3 that are applied to the DC motors 710, 720,730. Here, a phase to which the specific DC motor to be energized isconnected is defined as a “specific phase”, and a phase except for thespecific phase is defined as a “non-specific phase”.

When the steering lock actuator 710 is to be driven as the specific DCmotor, the determination is YES in S32, and the processing proceeds toS35A. In S35A, the motor phase currents Iu1#, Iv1#, Iw1# that areapplied to the three-phase winding set 801 and the current 11 that isapplied to the steering lock actuator 710 are computed by Formulas(1.1a) to (1.4a). In this case, the U1 phase is a specific phase, andthe V1 phase and the W1 phase are non-specific phases.

Iu1#=−Iv1−Iw1   (1.1a)

Iv1#=Iv1   (1.2a)

Iw1#=Iw1   (1.3a)

I1=Iu1−Iu1#  (1.4a)

In Formula (1.1a), the current value Iu1# of the current flowing throughthe U1 phase that is the specific phase is computed as an estimatedcurrent value by Kirchhoff's law from the current values Iv1, Iw1detected by the current sensors SAV1, SAW1 of the V1 phase and the W1phase that are the non-specific phases. In Formula (1.4a), the currentI1 flowing through the specific DC motor 710 is computed from theestimated current value Iu1# and the current value Iu1 detected by thecurrent sensor SAU of the U1 phase that is the specific phase.

FIG. 25 illustrates the waveforms of the inverter phase currents Iu1,Iv1, Iw1 flowing through the inverter 601. FIG. 26 illustrates thewaveforms of the motor phase currents Iu1#, Iv1#, Iw1# that are appliedto the three-phase winding set 801 in S35A. The inverter phase currentIu1 is offset from the motor phase current Iu1# indicated by a two-dotchain line, and this offset corresponds to the DC current I1.

When the tilt actuator 720 is to be driven as the specific DC motor, thedetermination is NO in S32 and YES in S33, and the processing proceedsto S35B. In S35B, the motor phase currents Iu1#, Iv1#, Iw1# that areapplied to the three-phase winding set 801 and the current I2 that isapplied to the tilt actuator 720 are computed by Formulas (1.1b) to(1.4b). In this case, the V1 phase is the specific phase, and the U1phase and the W1 phase are the non-specific phases. According toKirchhoff's law, the estimated current value Iv1# of the specific phaseis computed, and the current I2 flowing through the specific DC motor720 is computed from the estimated current value Iv1# and the detectedcurrent value Iv1 of the specific phase.

Iu1#=Iu1   (1.1b)

Iv1#=−Iu1−Iw1   (1.2b)

Iw1#=Iw1   (1.3b)

I2=Iv1−Iv1#  (1.4b)

When the telescopic actuator 730 is to be driven as the specific DCmotor, the determination is NO in S32, NO in S33, and YES in S34, andthe processing proceeds to S35C. In S35C, the motor phase currents Iu1#,Iv1#, Iw1# that are applied to the three-phase winding set 801 and thecurrent I3 that is applied to the telescopic actuator 730 are computedby Formulas (1.1c) to (1.4c). In this case, the W1 phase is the specificphase, and the U1 phase and the V1 phase are the non-specific phases.According to Kirchhoff's law, the estimated current value Iw1# of thespecific phase is computed, and the current I3 flowing through thespecific DC motor 730 is computed from the estimated current value Iw1#and the detected current value Iw1 of the specific phase.

Iu1#=Iu1   (1.1c)

Iv1#=Iv1   (1.2c)

Iw1#=−Iu1−Iv1   (1.3c)

I3=Iw1−Iw1#  (1.4c)

When the determination is NO in S34, none of the DC motors 710, 720, 730is driven, and the processing proceeds to S35D. In S35D, the motor phasecurrents Iu1#, Iv1#, Iw1# that are applied to the three-phase windingset 801 are computed by Formulas (1.1d) to (1.3d).

Iu1#=Iu1   (1.1d)

Iv1#=Iv1   (1.2d)

Iw1#=Iw1   (1.3d)

Next, phase voltage computation processing by the phase voltagecomputation unit 381 will be described with reference to flowcharts ofFIGS. 19 to 22 and voltage waveform diagrams of FIGS. 27A to 28B. FIG.19 illustrates phase voltage computation processing (I) for determiningthe energized phase of the inverter 601, and FIGS. 20 and 22 illustratetwo patterns of phase voltage computation processing (II) forcomputating the neutral point voltage Vn1 and the controlled phasevoltages Vu1#, Vv1#, Vw1# in accordance with the energization directionsof the DC motors 710, 720, 730. A first pattern of the phase voltagecomputation processing (II) may be combined with phase voltagecomputation processing (III) of FIG. 21. In the phase voltagecomputation processing (III), upper modulation processing or lowermodulation processing is performed on the basis of the controlled phasevoltages Vu1#, Vv1#, Vw1#. By this computation, the three-phase motor800 and any one of the DC motors 710, 720, 730 can be energizedsimultaneously, and the output ranges of the three-phase motor 800 andthe DC motors 710, 720, 730 can be increased within the restriction ofthe power supply voltage.

In the phase voltage computation processing (I), it is determinedwhether or not the output voltage of the three-phase motor 800 is lessthan a predetermined value in S31 of FIG. 19, and in the case of YES,the processing proceeds to S32. When the output voltage of thethree-phase motor 800 is equal to or larger than the predetermined valueand the determination is NO in S31, the control unit 30 gives priorityto ensuring the output voltage of the three-phase motor 800 and does notenergize the DC motors 710, 720, 730.

When the steering lock actuator 710 is to be driven, the determinationis YES in S32, and the processing proceeds to S36A and S37A. In S36A,the DC motor relays MV2 r/R and MW3 r/R are turned off, and MU1 r/R isturned on. In S37A, energization is performed in the U1 phase.

When the tilt actuator 720 is to be driven, the determination is NO inS32 and YES in S33, and the processing proceeds to S36B and S37B. InS36B, the DC motor relays MU1 r/R and MW3 r/R are turned off, and MV2r/R is turned on. In S37B, energization is performed in the V1 phase.

When the telescopic actuator 730 is to be driven, the determination isNO in S32, NO in S33, and YES in S34, and the processing proceeds toS36C and S37C. In S36C, the DC motor relays MU1 r/R, MV2 r/R are turnedoff, and MW3 r/R is turned on. In S37C, energization is performed in theW1 phase.

When the determination is NO in S31 or S34, none of the DC motors 710,720, 730 is driven, and the processing proceeds to S36D and S37D. InS36D, all the DC motor relays MU1 r/R, MV2 r/R, MW3 r/R are turned off,and in S37D, normal control, that is, energization of only thethree-phase motor 800, is performed.

The first pattern of the phase voltage computation processing (II) willbe described with reference to FIG. 20. Here, for example, when theinput voltage Vr1 or a reference voltage Vref for control of the DCmotor switches MU1H/L, MV2H/L, MW3H/L or the inverter 601 is 12 [V], VH,VM, and VL are set as default values, such as VH=10 [V], VM=6 [V], andVL=2 [V] (see FIGS. 28A and 28B).

When energization is to be performed in the positive direction, thedetermination is YES in S41, and the processing proceeds to S51F. InS51F, the neutral point voltage Vn1 is computed by Formula (2.1u) in thecase of the U1-phase energization, Formula (2.1v) in the case of theV1-phase energization, and Formula (2.1w) in the case of the W1-phaseenergization in accordance with the energized phase. In this way, thecontrol unit 30 adjusts the neutral point voltage Vn1 to be high.

Vn1=−Vu1+VH   (2.1u)

Vn1=−Vv1+VH   (2.1v)

Vn1=−Vw1+VH   (2.1w)

When energization is to be performed in the negative direction, thedetermination is NO in S41 and YES in S42, and the processing proceedsto S51R. In S51R, the neutral point voltage Vn1 is computed by Formula(2.2u) in the case of the U1-phase energization, Formula (2.2v) in thecase of the V1-phase energization, and Formula (2.2w) in the case of theW1-phase energization in accordance with the energized phase. In thisway, the control unit 30 adjusts the neutral point voltage Vn1 to below.

Vn1=−Vu1+VL   (2.2u)

Vn1=−Vv1+VL   (2.2v)

Vn1=−Vw1+VL   (2.2w)

When no energization is performed either in the positive or negativedirection, the determination is NO in S41 and NO in S42, and theprocessing proceeds to S51N. In S51N, the neutral point voltage Vn1 iscomputed by Formula (2.3).

Vn1=VM   (2.3)

In cases where the phase voltage computation processing (III) is notperformed after S51F, S51R, and S51N, the processing proceeds to S54 incommon. In a case where the phase voltage computation processing (III)is performed, the processing is linked to FIG. 21 via link symbols F, R,N as indicated by broken line arrows. In S54, the neutral point voltageVn1 is added to the voltage commands Vu1, Vv1, Vw1 of the respectivephases by Formulas (3.1) to (3.3), and the controlled voltages Vu1#,Vv1#, Vw1# are computed. Here, the phase voltage computation unit 381 ofthe control block diagram illustrated in FIG. 15 computes the phasevoltage with VH and VL as fixed values regardless of the phase voltageamplitude.

As illustrated in FIG. 27A, each of the voltage commands Vu1, Vv1, Vw1before the phase voltage computation processing, output from thetwo-phase to three-phase conversion unit 371, has a sinusoidal shapecentered around 0 [V]. When the DC motors 710, 720, 730 are stopped, asillustrated in FIG. 27B, the phase voltage computation unit 381 outputsa controlled voltage command centered around VM (6 [V]).

When the DC motors 710, 720, 730 are driven, the phase voltagecomputation unit 381 shifts the neutral point voltage Vn1 of thethree-phase motor 800. As illustrated in FIG. 28A, when the U1 phase isto be energized in the positive direction, VH to be the controlledvoltage Vu1# of the energized phase is constant at 10 [V]. Asillustrated in FIG. 28B, when the U1 phase is to be energized in thenegative direction, VL to be the controlled voltage Vu1# of theenergized phase is constant at 2 [V].

Vu1#=Vu1+Vn1   (3.1)

Vv1#=Vv1+Vn1   (3.2)

Vw1#=Vw1+Vn1   (3.3)

Although FIGS. 28A and 28B illustrate the examples in which the phasevoltage amplitude of the waveform is 12 [V], VH in the computation ofthe DC motor terminal voltage and the upper limit of the voltage outputto the three-phase motor in the phase voltage computation processing (I)may be determined such that the maximum value of the phase voltageamplitude is about 11 [V] in consideration of the ON time of the lowerarm element for current detection.

Although FIGS. 28A and 28B illustrate the examples in which the upperlimit of the phase voltage amplitude of the waveform is 12 [V] and thelower limit is 0 [V], VH in the computation of the DC motor terminalvoltage and the upper limit of the voltage output to the three-phasemotor in the phase voltage computation processing (I) may be determinedsuch that the upper limit of the phase voltage amplitude is about 11.76[V] and the lower limit is about 0.24 [V] in consideration of the ONtime of the lower arm element or the upper arm element.

Moreover, a configuration in which the control unit 30 adjusts theneutral point voltage Vn1 in accordance with the voltage that is appliedto the three-phase motor 800 will be described with reference to FIGS.29 to 31B. In the control block diagram of FIG. 29, an amplitudecomputation unit 373 is added to FIG. 15. The amplitude computation unit373 computes the phase voltage amplitude by the following formula on thebasis of the dq-axis voltage commands Vd1, Vq1. As indicated by atwo-dot chain line, the amplitude computation unit 373 may compute thephase voltage amplitude on the basis of the dq-axis current commandvalues Id1**, Iq1** or may compute the phase voltage amplitude on thebasis of the current detection value or the rotational speed.

Phase voltage amplitude=√(2/3)×√(Vd1² +Vq1²)

The phase voltage computation unit 381 computes VH and VL by thefollowing formulas. V max is 12 [V] that is the input voltage Vr1 or thereference voltage Vref for control, or a voltage (e.g., 93% of 12[V]=11.16 [V]) in consideration of current detection by the currentsensors SAU1, SAV1, SAW1 on the low potential side. V min is 0 [V] or avoltage (e.g., 4% of 12 [V]=0.48 [V]) in consideration of the pre-driveroutput.

VH=V max−(√3)×phase voltage amplitude

VL=V min+(√3)×phase voltage amplitude

FIGS. 30A to 31B illustrate examples in which the phase voltageamplitude increases with a constant gradient over three electrical angleperiods (1080 [deg]). As illustrated in FIG. 30A, each of the voltagecommands Vu1, Vv1, Vw1 before the phase voltage computation processing,output from the two-phase to three-phase conversion unit 371, has asinusoidal shape in which the amplitude gradually increases around 0[V]. When the DC motors 710, 720, 730 are stopped, as illustrated inFIG. 30B, the phase voltage computation unit 381 outputs a controlledvoltage command centered around VM (6 [V]).

When the DC motors 710, 720, 730 are driven, the phase voltagecomputation unit 381 shifts the neutral point voltage Vn1 of thethree-phase motor 800. As illustrated in FIG. 31A, when the U1 phase isto be energized in the positive direction, VH to be the controlledvoltage Vu1# of the energized phase gradually decreases from 12 [V] toabout 10 [V] as the phase voltage amplitude increases. The maximumvalues of the voltages Vv1#, Vw1# of the V1 phase and the W1 phase are12 [V]. As illustrated in FIG. 31B, when the U1 phase is to be energizedin the negative direction, VH to be the controlled voltage Vu1# of theenergized phase gradually increases from 0 [V] to about 2 [V] as thephase voltage amplitude increases. The minimum values of the voltagesVv1#, Vw1# of the V1 phase and the W1 phase are 0 [V].

Returning to FIG. 20, in S55, the control unit 30 causes the inverterswitching elements IU1H/L, IV1H/L, IW1H/L to perform a switchingoperation so as to output the controlled voltages Vu1#, Vv1#, Vw1#.

Next, the phase voltage computation processing (III) will be describedwith reference to a flowchart of FIG. 21. Following the link symbols F,R, N, S54 is executed as in the first embodiment. When energization isto be performed in the positive direction, in S56F, the maximum values Vmax of the controlled voltages Vu1#, Vv1#, Vw1# of the respective phasesare computed by Formula (5.1). In S57F, a neutral point control voltageVnn of the upper modulation processing is computed by Formula (5.2).Twelve [V] in Formula (5.2) may be the inverter input voltage Vr1, andis computed such that a duty ratio of the phase having the maximumvoltage is 100% or a value close to 100%.

V max=MAX(Vu1#,Vv1#,Vw1#)   (5.1)

Vnn=12[V]−V max   (5.2)

When energization is to be performed in the negative direction, in S56R,the minimum values V min of the controlled voltages Vu1#, Vv1#, Vw1# ofthe respective phases are computed by Formula (5.3). In S57R, theneutral point control voltage Vnn of the lower modulation processing iscomputed by Formula (5.4).

V min=MIN(Vu1#,Vv1#,Vw1#)   (5.3)

Vnn=0[V]−V min   (5.4)

In common with the upper modulation processing and the lower modulationprocessing, in S58, the neutral point control voltage Vnn is added tothe controlled voltages Vu1#, Vv1#, Vw1# of the respective phases inaccordance with Formulas (6.1) to (6.3), and the respective phasevoltages Vu1##, Vv1##, Vw1## after the correction of the neutral pointvoltage are computed.

Vu1##=Vu1#+Vnn   (6.1)

Vv1##=Vv1#+Vnn   (6.2)

Vw1##=Vw1#+Vnn   (6.3)

When no energization is performed either in the positive or negativedirection, in S57N indicated by a broken line, the upper modulationprocessing or the lower modulation processing may be performed, orneither processing may be performed. In S59, the control unit 30 causesthe inverter switching elements IU1H/L, IV1H/L, IW1H/L to perform theswitching operation so as to output the respective phase voltages Vu1##,Vv1##, Vw1## after the correction of the neutral point voltage.

Next, a second pattern of the phase voltage computation processing (II)will be described with reference to FIGS. 22. S41, S42, and S51N are thesame as in the first pattern. In both S52F and S52R, in accordance withthe energized phase, the neutral point voltage Vn1 is computed on thebasis of the DC motor terminal voltages Vm1, Vm2, Vm3 and the DC motorapplied voltage Vx by Formula (4.1u) in the case of the U1-phaseenergization, by Formula (4.1v) in the case of the V1-phaseenergization, and by Formula (4.1w) in the case of the W1-phaseenergization.

Vn1=Vm1+Vx−Vu1   (4.1u)

Vn1=Vm2+Vx−Vv1   (4.1v)

Vn1=Vm3+Vx−Vw1   (4.1w)

In common S54 following S52F, S52R, and S51N, the controlled voltagesVu1#, Vv1#, Vw1# of the respective phases are computed similarly to thefirst pattern. For example, when the U1 phase is to be energized, thecontrolled voltage Vu1# is “Vm1+Vx” regardless of the energizationdirection. S55 is the same as in the first pattern. The phase voltagecomputation processing (III) is not applied to the second pattern of thephase voltage computation processing (II).

Next, a first pattern of the DC motor terminal voltage computationprocessing will be described with reference to FIG. 23. This firstpattern is combined with the first pattern of the phase voltagecomputation processing (II). S31 to S34 are the same as those in thephase voltage computation processing (I) of FIG. 19. Normally, at aninitial stage, all the DC motor switches MU1H/L, MV2H/L, MW3H/L areturned off. Hereinafter, “turning off the switch” includes not only thecase of turning off the switch to shift from an ON state to an OFF statebut also the case of maintaining the switch in the initial OFF state. Bythis computation, the three-phase motor 800 and any one of the DC motors710, 720, 730 can be energized simultaneously, and the output ranges ofthe three-phase motor 800 and the DC motors 710, 720, 730 can beincreased within the restriction of the power supply voltage.

When the steering lock actuator 710 is to be driven, in S47A, the DCmotor terminal voltage Vm1 is computed by Formula (7.1a). The controlunit 30 causes the DC motor switch MU1H/L to perform the switchingoperation so as to output the DC motor terminal voltage Vm1 in S48A, andturns off the DC motor switches MV2H/L, MW3H/L in S49A.

When the tilt actuator 720 is to be driven, in S47B, the DC motorterminal voltage Vm2 is computed by Formula (7.1b). The control unit 30causes the DC motor switch MV2H/L to perform the switching operation soas to output the DC motor terminal voltage Vm2 in S48B, and turns offthe DC motor switches MU1H/L, MW3H/L in S49B.

When the telescopic actuator 730 is to be driven, in S47C, the DC motorterminal voltage Vm3 is computed by Formula (7.1c). The control unit 30causes the DC motor switch MW3H/L to perform the switching operation soas to output the DC motor terminal voltage Vm3 in S48C and turns off theDC motor switches MU1H/L, MV2H/L in S49C. When the phase voltagecomputation processing (III) is not performed, Vu1## is replaced withVu1#, Vv1## is replaced with Vv1#, and Vw1## is replaced with Vw1#.

Vm1=Vu1##−Vx   (7.1a)

Vm2=Vv1##−Vx   (7.1b)

Vm3=Vw1##−Vx   (7.1c)

When the determination is NO in S31 or S34, none of the DC motors 710,720, 730 is driven, and all the DC motor switches MU1H/L, MV2H/L, MW3H/Lare turned off in S49D.

A second pattern of the DC motor terminal voltage computation processingwill be described with reference to FIG. 24. The second pattern may becombined with the second pattern of the phase voltage computationprocessing (II) or may be combined with the first pattern. Incombination with the second pattern, the phase voltage computationprocessing (II) is performed after the DC motor terminal voltagecomputation processing is performed, and in combination with the firstpattern, the phase voltage computation processing (II) is performedbefore the DC motor terminal voltage computation processing isperformed. By this computation, the three-phase motor 800 and any one ofthe DC motors 710, 720, 730 can be energized simultaneously, and theoutput ranges of the three-phase motor 800 and the DC motors 710, 720,730 can be increased within the restriction of the power supply voltage.

S31 to S34 are the same as those in FIGS. 19 and 23. When the steeringlock actuator 710 is to be driven and the energization direction is thepositive direction, the determination is YES in S41A. In S43A, the DCmotor switch MU1L on the low potential side is turned on, and the DCmotor switch MU1H on the high potential side is turned off. In S45A,“Vm1=12 [V] or the inverter input voltage Vr1” is computed. In the fifthembodiment, the input voltage Vrd from another power supply Btd is usedinstead of the inverter input voltage Vr1. The same applies to S45B andS45C. On the other hand, when the energization direction is the negativedirection, the determination is NO in S41. In S44A, the switch MU1L onthe low potential side is turned off, and the switch MU1H on the highpotential side is turned on. In S46A, “Vm1=0 [V]” is computed. S48A andS49A to which the processing proceeds after S45A or S46A are the same asthose in FIG. 23.

For example, the description will be given in combination with S51F andS51R of the first pattern in the phase voltage computation processing(II) illustrated in FIG. 20. when energizing the specific DC motor 710in the positive direction, the control unit 30 turns on the DC motorswitch MU1L on the low potential side connected to the second terminalor causes the DC motor switches MU1H/L on the low potential side and thehigh potential side connected to the second terminal T2 to perform theswitching operation such that the voltage of the second terminal T2 islower than the voltage of the first terminal T1, and controls theneutral point voltage Vn1 of the three-phase winding set 801 to behigher. When energizing the specific DC motor 710 in the negativedirection, the control unit 30 turns on the DC motor switch MU1H on thehigh potential side connected to the second terminal or causes the DCmotor switches MU1H/L on the low potential side and the high potentialside connected to the second terminal T2 to perform the switchingoperation such that the voltage of the second terminal T2 is higher thanthe voltage of the first terminal T1, and controls the neutral pointvoltage Vn1 of the three-phase winding set 801 to be lower. Since theapplied voltage Vx is not used, the computation amount of the controlunit 30 can be reduced. In addition, only turning on and off the DCmotor switch MU1H/L simplifies the operation, which can facilitatefinding an abnormality.

When the tilt actuator 720 is to be driven and the energizationdirection is the positive direction, the determination is YES in S41B.In S43B, the DC motor switch MV2L on the low potential side is turnedon, and the DC motor switch MV2H on the high potential side is turnedoff. In S45B, “Vm2=12 [V] or the inverter input voltage Vr1” iscomputed. On the other hand, when the energization direction is thenegative direction, the determination is NO in S41. In S44B, the switchMV2Lh on the low potential side is turned off, and MV2H on the highpotential side is turned on. In S46B, Vm2=0 [V]” is computed. S45B andS46B to which the processing proceeds after S48B or S49B are the same asthose in FIG. 23.

When the telescopic actuator 730 is to be driven, the determination isYES in S41C when the energization direction is the positive direction.In S43C, the DC motor switch MW3L on the low potential side is turnedon, and the DC motor switch MW3H on the high potential side is turnedoff. In S45C, “Vm3=12 [V] or the inverter input voltage Vr1” iscomputed. On the other hand, when the energization direction is thenegative direction, the determination is NO in S41. In S44C, the switchMW3L on the low potential side is turned off, and MW3H on the highpotential side is turned on. In S46C, “Vm3=0 [V]” is computed. S45C andS46C to which the processing proceeds after S48C or S49C are the same asthose in FIG. 23. S49D, to which the processing proceeds when thedetermination is NO in S31 or S34, is also the same as that in FIG. 23.

Next, a third pattern different from the above two patterns related tothe phase voltage computation processing (II) will be described withreference to FIGS. 32 and 33. This third pattern is combined with thefirst pattern of the DC motor terminal voltage computation processing.By this computation, the three-phase motor 800 and any one of the DCmotors 710, 720, 730 can be energized simultaneously, and the outputranges of the three-phase motor 800 and the DC motors 710, 720, 730 canbe increased within the restriction of the power supply voltage.

In a flowchart of FIGS. 32, S41 and S42 are the same as in the first andsecond patterns of the phase voltage computation processing (II). InS53F at the time of energization in the positive direction, the neutralpoint voltage Vn1 is computed by Formula (8.1) regardless of theenergized phase. In S53R at the time of energization in the negativedirection, the neutral point voltage Vn1 is computed by Formula (8.2)regardless of the energized phase.

Vn1=VH   (8.1)

Vn1=VL   (8.2)

S51N, S54, and S55 are the same as in the first and second patterns ofthe phase voltage computation processing (II). In addition, as in thefirst pattern, the processing may be linked to the phase voltagecomputation processing (III) in FIG. 21 via the link symbols F, R, N. Asillustrated in FIG. 33, in the third pattern, for example, thecontrolled voltage Vu1# of the U1 phase is not set to a constant voltagebut is shifted by constant VH, VL, or VM with respect to the voltagecommand Vu1.

Since the computation processing in each pattern described above isconfigured to apply a voltage to each of the DC motors 710, 720, 730when there is a margin of voltage for shifting the neutral point voltageVn1, each of the DC motors 710, 720, 730 preferably has a small outputwith respect to the three-phase motor 800. In addition, each of the DCmotors 710, 720, 730 preferably has a smaller current to be applied,larger resistance, and a larger time constant than the three-phase motor800.

Next, an operation immediately after the turning-on of the vehicleswitch will be described with reference to a flowchart of FIG. 34 and acircuit configuration diagram of FIG. 35. FIG. 35 illustrates a state inwhich the tilt actuator 720 and the telescopic actuator 730 areenergized in the configuration of FIG. 6 of the second embodiment. Here,a description will be given assuming that DC motor relays MU1 r/R, MV2r/R, MW3 r/R are not present. In the configuration including the DCmotor relays MU1 r/R, MV2 r/R, MW3 r/R, it is assumed that the DC motorrelays MU1 r/R, MV2 r/R, MW3 r/R are turned on at least at the time ofenergization of the corresponding DC motor.

In the present embodiment, there is a request to move the tilt andtelescopic positions to the stored positions as soon as possibleimmediately after the turning-on of the vehicle switch illustrated inS01 of FIG. 17. Therefore, when the absolute value |Ts| of the steeringtorque is low and the vehicle speed V is low, the three-phase motor 800is not energized, and the plurality of DC motors 710, 720, 730 areenergized simultaneously. A completion flag 1 in FIG. 34 is off whilethe steering is locked, and the flag is turned on when the steering lockis released. A completion flag 2 is off when the tilt is at a positionexcept for the stored position, and the flag is turned on when the tiltreaches the stored position. A completion flag 3 is off when thetelescopic is at a position except for the stored position, and the flagis turned on when the telescopic reaches the stored position. In S71immediately after the turning-on of the vehicle switch, all of thecompletion flag 1, the completion flag 2, and the completion flag 3 areset to off as initial values.

In S72, the control unit 30 turns off all the DC motor switches MU1H,MV2H, MW3H on the high potential side, turns on all the DC motorswitches MU1L, MV2L, MW3L on the low potential side, turns on theinverter switching elements IU1H, IV1H, IW1H on the high potential sideof all phases, and turns off the inverter switching elements IU1L, IV1L,IW1L on the low potential side of all phases. S73 and subsequent stepswill be described on the premise of this initial state. Thus, thethree-phase motor 800 is not energized, and the DC motors 710, 720, 730can be energized simultaneously.

As another method, the control unit 30 may turn on all the DC motorswitches MU1H, MV2H, MW3H on the high potential side, turn off all theDC motor switches MU1L, MV2L, MW3L on the low potential side, turn offthe inverter switching elements IU1H, IV1H, IW1H on the high potentialside of all phases, and turn on the inverter switching elements IU1L,IV1L, IW1L on the low potential side of all phases. When the DC motor isconnected to only one phase or two phases of the three phases, or whenonly the DC motor connected to one phase or two phases is energized,“all phases” described above for the inverter switching elements isreplaced with “a phase to which the DC motor is connected”.

When it is desired to change the energization direction of each of theDC motors 710, 720, 730 in accordance with the condition of the tilt ortelescopic position or the like, the following may be performed. First,the inverter switching elements IU1H, IV1H, IW1H on the high potentialside and the inverter switching elements IU1L, IV1L, IW1L on the lowpotential side are caused to perform the switching operation at the sameduty ratio, for example, 50%. In accordance with the direction in whicheach DC motor is desired to be energized, the DC motor switches MU1H,MV2H, MW3H on the high potential side are turned off and the DC motorswitches MU1L, MV2L, MW3L on the low potential side are turned on, orthe inverter switching elements IU1H, IV1H, IW1H on the high potentialside are turned on and the inverter switching elements IU1L, IV1L, IW1Lon the low potential side are turned off.

By causing the inverter switching elements IU1H/L, IV1H/L, IW1H/L ofeach phase to perform the switching operation at the same duty ratio orturning off the inverter switching elements on the high potential sideand the low potential side to stop the energization of the three-phasemotor 800, and by changing the DC motor terminal voltages Vm1, Vm2, Vm3by the switching or the switching operation of the DC motor switchesMU1H/L, MV2H/L, MW3H/L, it is possible to simultaneously energize the DCmotors 710, 720, 730 without energizing the three-phase motor 800.

In S73, it is determined whether the steering lock has been released orthe completion flag 1 is on. In the case of YES in S73, the DC motorswitch MU1L and the inverter switching element IU1H are turned off inS741. At this time, the completion flag 1 is on. FIG. 35 illustrates acurrent path at this time. In the case of NO in S73, MU2L and IU1H aremaintained in the ON state in S742, and the energization of the steeringlock actuator 710 is continued.

In S75, it is determined whether the tilt has reached the storedposition or the completion flag 2 is on. In the case of YES in S75, theDC motor switch MV2L and the inverter switching element IV1H are turnedoff in S761. At this time, the completion flag 2 is on. In the case ofNO in S75, MV2L and IV1H are maintained in the ON state in S762, and theenergization of the tilt actuator 720 is continued.

In S77, it is determined whether the telescopic has reached the storedposition or the completion flag 3 is on. In the case of YES in S77, theDC motor switch MW3L and the inverter switching element IW1H are turnedoff in S781. At this time, the completion flag 3 is on. In the case ofNO in S77, the ON states of MW3L and IW1H are maintained in S782, andthe energization of the telescopic actuator 730 is continued.

In S79, it is determined whether all of the completion flag 1, thecompletion flag 2, and the completion flag 3 are on. In a case where allthe completion flags 1 to 3 are on and the determination is YES in S79,the processing ends. On the other hand, when any one of the completionflag 1, the completion flag 2, and the completion flag 3 is off, thedetermination is NO in S79, the processing returns to before S73, andthe determination steps of S73, S75, and S77 are repeated.

Next, control related to the drive and stop of the DC motor during thedrive of the three-phase motor will be described with reference to FIGS.36 to 40. In the description of this portion, only “710” is used as thereference character of the DC motor. Although not mentioned in the abovedescription, it is assumed that the control unit 30 detects anabnormality such as an overcurrent abnormality in the inverter 601 orthe three-phase motor 800.

FIG. 36 illustrates a flowchart for switching between the drive and stopof the DC motor 710 during the drive of the three-phase motor 800. Thecontrol unit 30 switches between the drive and stop of the DC motor 710by controlling the neutral point voltage Vn1 on the basis ofpredetermined conditions described below. In S91, it is determinedwhether the vehicle switch 11 is off, that is, whether it is a vehiclestopping period, and in the case of YES, the control unit 30 ends theprocessing. When the vehicle switch 11 is on and the determination is NOin S91, the processing proceeds to S92.

In step S92, as “ON determination”, the start of the energization of theDC motor 710 is determined in accordance with the AND condition of eachof the following items. When the conditions of all the items aresatisfied, the determination is YES in S92, and the processing proceedsto “ON processing” in S93 to S95. When the condition of even one item isnot satisfied, the processing returns to before S91.

[1] Drive signal=ON.

[2] The phase voltage amplitude is smaller than a threshold Vth1, andthe phase current amplitude is smaller than a threshold Ith1.

[3] The abnormality of the inverter 601 or the three-phase motor 800 hasnot been detected, that is, the inverter 601 and the three-phase motor800 are normal.

The drive signal in [1] is turned on when the initial drive is performedat the start of the vehicle, when there is a request for releasing thesteering lock by the driver's operation, when a command signal fordriving the DC motor 710 is notified from another ECU, or the like. Inthe case of the DC motors 720, 730, the drive signal is turned on whenthere is an input in the tilt switch 12 or the telescopic switch 13.

[2] indicates that there is a margin in the output of the inverter 601.When the phase voltage amplitude is smaller than the threshold Vth1 andthe phase current amplitude is smaller than the threshold Ith1, it isdetermined that there is a margin for distributing power to the DC motor710 because the power supply to the three-phase motor 800 is small. Itis sufficient that the phase voltage amplitude is a value correlatedwith the amplitude of the phase voltage command and that the phasecurrent amplitude is a value correlated with the amplitude of the actualphase current. For example, the rotational speed of the three-phasemotor 800 may be used as a value correlated with the phase voltageamplitude or the phase current amplitude. A current command value may beused as the phase current amplitude. The determination may be performedon all of [1], [2] and [3] or may be performed some of [1], [2] and [3].The determination may be performed on the basis of the absolute value|Ts| of the steering torque or the vehicle speed V described withreference to FIG. 17.

In S93 of the ON processing, a fail-safe threshold switching flag for afail-safe threshold in the abnormality detection of the inverter 601 orthe three-phase motor 800 is turned on. Thereby, the control unit 30increases the threshold for determining the overcurrent for thethree-phase current by the amount of the current assumed to flow throughthe DC motor 710. In addition to the fail-safe threshold in theabnormality detection for the three-phase motor 800, a fail-safethreshold in the abnormality detection for the circuit or the DC motor710 may be set. In S94, a current detection switching flag is turned on.In S95, “energization start processing for the DC motor” correspondingto the period from time t1 to time t3 in FIGS. 39 and 40 is executed,and the DC motor 710 is driven.

As thus described, the control unit 30 switches the fail-safe thresholdin the abnormality detection between when the DC rotating machine DCmotor 710 is driven and when the motor is not driven. FIGS. 37 and 38illustrate Flowchart Examples 1 and 2 of the fail-safe thresholdswitching. In Example 1 illustrated in FIG. 37, when the fail-safethreshold switching flag is off in S930, the fail-safe threshold is setto A in S931, and when the fail-safe threshold switching flag is on, thefail-safe threshold is set to B (>A) in S932.

In Example 2 illustrated in FIG. 38, when the fail-safe thresholdswitching flag is off in S930, it is determined in S933 whether theabsolute value (|Iu1+Iv1+Iw1|) of the sum of the three-phase currents islarger than C. When the fail-safe threshold switching flag is on, it isdetermined in S934 whether the absolute value (|Iu1+Iv1+Iw1|) of the sumof the three-phase currents is larger than (C+D). In the case of YES inS933, the control unit 30 increments an abnormal-time counter in S935.In the case of YES in S934, the control unit 30 increments theabnormal-time counter in S936.

The flowchart of the phase current computation of FIG. 18. is referredto for the processing when the current detection switching flag isturned on. That is, when the current detection switching flag is on,motor phase currents Iu#, Iv#, Iw# and DC currents I1, I2 are computedby the formulas of S35A, S35B, and S35C. On the other hand, when thecurrent detection switching flag is off, the motor phase currents Iu#,Iv#, Iw# are computed by the formula of S35D.

Returning to FIG. 36, in S96, as “OFF determination”, the end of theenergization of the DC motor 710 is determined in accordance with the ORcondition of each of the following items. When the condition of at leastone item is satisfied, the determination is YES in S96, and theprocessing proceeds to “OFF processing” in S97 to S99. When thecondition of any item is not satisfied, the processing returns to beforeS96.

[1] Drive signal=Off.

[2] The phase voltage amplitude is larger than a threshold Vth2, or thephase current amplitude is larger than a threshold Ith2.

[3] The abnormality of the inverter 601 or the three-phase motor 800 isdetected.

The drive signal in [1] is turned off when the request for releasing thesteering lock is ended, when a command signal for stopping the DC motor710 is notified from another ECU, or the like. In the case of the DCmotors 720, 730, the drive signal is turned off when the tilt switch 12or the telescopic switch 13 is turned off.

[2] indicates that there is no margin in the output of the inverter 601.When the phase voltage amplitude is larger than the threshold Vth2 orthe phase current amplitude is larger than the threshold Ith2, it isdetermined that there is no margin for distributing output to the DCmotor 710 because the power supply to the three-phase motor 800 islarge. ON/OFF hysteresis may be provided by setting thresholds for ONdetermination and OFF determination to Vth1<Vth2 and Ith1<Ith2. Thedetermination may be performed on all of [1], [2] and [3] or may beperformed some of [1], [2] and [3]. The determination may be performedon the basis of the absolute value |Ts| of the steering torque or thevehicle speed V described with reference to FIG. 17.

In the OFF processing, processing in a reverse order to the ONprocessing is performed. In S97, “energization end processing for the DCmotor” corresponding to the period from time t4 to time t6 in FIGS. 39and 40 is executed, and the DC motor 710 is stopped. In S98, the currentdetection switching flag is turned off. In S99, the fail-safe thresholdswitching flag is turned off. Thus, the threshold changed while the DCmotor 710 is energized is returned to the original value. Thereafter,the processing returns to before S91, and the routine is repeated.

In the flowchart of FIG. 36, the sequence in which the OFF determinationis executed after the completion of the ON processing has beendescribed, but the processing may proceed to the OFF processing when thecondition of the OFF determination is satisfied during the energizationstart processing for the DC motor 710. Conversely, when the ONdetermination is satisfied during the energization end processing forthe DC motor, the processing may proceed to the ON processing. Inaddition, in order to avoid switching back and forth between the ON andOFF states, it may be configured that the ON determination is notaccepted again for a predetermined period (e.g., about several 100 [ms])after the OFF processing.

FIGS. 39 and 40 illustrate changes in each phase voltage of the inverter601, ON/OFF of the DC motor switch on the low potential side, andchanges in the DC current I1 flowing through the DC motor 710 as ControlExamples 1 and 2 at the time of the drive and stop of the DC motor 710during the drive of the three-phase motor 800. As indicated by thevertical axis of each phase voltage, each phase voltage may be convertedinto a duty ratio with 12 [V] as 100%. In addition, the DC motor switchon the low potential side will be abbreviated as a “lower switch”, andonly “MU1L” will be described as a reference character.

First, detailed differences between Control Examples 1 and 2 will beignored, and the overall operation will be described. As a main target,at the time of stopping the drive of the DC motor 710, the control unit30 reduces the current on the inverter 601 side and then turns off thelower switch MU1L. Therefore, as described with reference to FIG. 36,for example, when the phase voltage amplitude is equal to or larger thanthe threshold Vth1 at the time of ON determination, the control unit 30does not energize the DC motor 710. When the phase voltage amplitudeexceeds the threshold Vth2 during the energization of the DC motor 710,the control unit 30 ends the energization of the DC motor 710. Thethresholds Vth1 and Vth2 are preferably set to voltage values having amargin in consideration of times required for the start and stop.

The average value, or the average equivalent value of each phase voltagein the three-phase motor 800 decreases from 6 [V] to VLx close to 0 [V](e.g., about 1 [V]) at time t1, then increases from VLx when the lowerswitch MU1L is turned on at time t2, and reaches VHx close to 12 [V](e.g., about 11 [V]) at time t3. At this time, the DC current increasesfrom 0 to the maximum value I₁₀₀ as each phase voltage changes, and isthen maintained in that state.

When it is determined that the energization of the DC motor 710 ends,the control unit 30 controls the inverter switching elements IU1H/L,IV1H/L, IW1H/L at time t4 so as to lower the respective phase voltages.At time t6 after time t5 when the average value or the averageequivalent value of each phase voltage decreases to VLx, the controlunit 30 turns off the lower switch MU1L. To put it simply, the controlunit 30 turns off the lower switch MU1L after reducing the current suchthat the current on the inverter 601 side decreases gradually.

As thus described, at the time of stopping the DC motor 710, the controlunit 30 controls the inverter switching elements IU1H/L, IV1H/L, IW1H/Lso as to lower the voltage on the first terminal T1 side of the DC motor710 and then turns off the lower switch MU1L to end the energization ofthe DC motor 710. As a result, even when a switch having a relativelysmall current capacity is used for the DC motor switch MU1H/L, it ispossible to prevent the lower switch MU1L from being overloaded at thestop of the energization. In addition, a transistor or a mechanicalrelay that performs a slow switching operation can be used on thepremise that a high-speed switching operation is not performed.

Next, there is a difference between Control Example 1 and ControlExample 2 in the phase voltage computation of the U1 phase, which is theenergized phase, in the period immediately before the turning-on of thelower switch MU1L and the period before and after the turning-off of thelower switch MU1L, that is, the period from time t1 to time t2 and theperiod from time t5 to time t7. In Control Example 1, the neutral pointvoltage Vn1 is shifted such that the phase voltage Vu1# of the U1 phase,which is the energized phase, is constant. In this case, the U1-phasevoltage Vu1# does not completely become 0 [V] at times t2 and t6 whenthe lower switch MU1L is turned on or off. During the period from timet5 to time t6 before the turning-off of the lower switch MU1L, the DCcurrent I1 corresponding to the constant phase voltage Vu1# flows.

In Control Example 2, during the period from time t1 to time t2 and fromtime t5 to time t7, the neutral point voltage Vn1 is shifted while thethree-phase voltage is kept as a sine wave. As illustrated in the lowerenlarged view, the control unit 30 turns on or off the lower switch MU1Lat the timing when the U1-phase voltage Vu1# is exactly 0 [V] (or theduty ratio of the U1 phase is exactly 0 [%]) or at the timing when thedetection current becomes 0 or the current becomes 0 in consideration ofthe delay of the time constant of the energization path. The controlunit 30 starts increasing each phase voltage after the lapse of theminute time δT from time t2. During the period from time t5 to time t6before the turning-off of the lower switch MU1L, the DC current I1corresponding to the sinusoidal phase voltage Vu1# flows. In ControlExample 2, the voltage applied from the inverter 601 when the lowerswitch MU1L is turned on or off can be ideally set to 0.

[Circuit Configuration in which Two-System Three-Phase Motor is Driven]

Next, an embodiment in which the three-phase motor 800 having atwo-system configuration is a drive target will be described. First,concerning the structure of the three-phase motor 800, a configurationexample of an “electromechanical integrated motor” in which the ECU 10is integrally configured on one side in the axial direction will bedescribed with reference to FIGS. 41 and 42. In the embodimentillustrated in FIG. 41, the ECU 10 is disposed coaxially with an axis Axof a shaft 87 on the side opposite to the output side of the three-phasemotor 800. In another embodiment, the ECU 10 may be configuredintegrally with the three-phase motor 800 on the output side of thethree-phase motor 800. The three-phase motor 800 is a brushless motorand includes a stator 840, a rotor 860, and a housing 830 thataccommodates the stator 840 and the rotor 860.

The stator 840 includes a stator core 844 fixed to the housing 830 andtwo three-phase winding sets 801, 802 assembled to the stator core 844.Lead wires 851, 853, 855 extend from the respective phase windingsconstituting a first-system three-phase winding set 801 (hereinafterreferred to as “first three-phase winding set”) 801. Lead wires 852,854, 856 extend from the respective phase windings constituting asecond-system three-phase winding set (hereinafter referred to as“second three-phase winding set”) 802. The phase windings are woundabout respective slots 848 of the stator core 844.

The rotor 860 includes the shaft 87, supported by a rear bearing 835 anda front bearing 836, and a rotor core 864 fitted with the shaft 87. Therotor 860 is provided inside the stator 840 and is rotatable relative tothe stator 840. At one end of the shaft 87, a permanent magnet 88 fordetecting a rotational angle is provided.

The housing 830 has a bottomed cylindrical case 834 including a rearframe end 837, and a front frame end 838 provided at one end of the case834. The case 834 and the front frame end 838 are fastened to each otherby bolts or the like. The lead wires 851, 852, and the like of therespective three-phase winding sets 801, 802 are inserted through leadwire insertion holes 839 of the rear frame end 837, extend toward theECU 10, and are connected to a substrate 230.

The ECU 10 includes a cover 21, a heatsink 22 fixed to the cover 21, thesubstrate 230 fixed to the heatsink 22, and various electroniccomponents mounted on the substrate 230. The cover 21 protects theelectronic components from external impact and prevents the entry ofdust, water, and the like into the ECU 10. The cover 21 includes aconnector portion 214 for external connection with a feed cable and asignal cable from the outside, and a cover portion 213. Feedingterminals 215, 216 of the connector portion 214 for external connectionare connected to the substrate 230 via a path (not illustrated). Notethat the connector is denoted by a reference character different fromthat in FIG. 4.

The substrate 230 is, for example, a printed board, is provided at aposition facing the rear frame end 837, and is fixed to the heatsink 22.On the substrate 230, the electronic components for the two systems areprovided independently for the respective systems. The number of thesubstrates 230 is not limited to one but may be two or more. Of the twomain surfaces of the substrate 230, the surface facing the rear frameend 837 is taken as a motor surface 237, and the opposite surface, thatis, the surface facing the heatsink 22, is taken as a cover surface 238.

On the motor surface 237, a plurality of switching elements 241, 242,rotational angle sensors 251, 252, custom integrated circuits (ICs) 261,262, and the like are mounted. The plurality of switching elements 241,242 correspond to IU1H/L or the like in each configuration diagram ofthe ECU and constitute the three-phase upper and lower arms of therespective systems. The rotational angle sensors 251, 252 are disposedso as to face the permanent magnet 88 provided at the tip of the shaft87. The custom ICs 261, 262 and microcomputers 291, 292 each have acontrol circuit of the ECU 10. The two rotational angle sensors 251,252, the microcomputers 291, 292, and the like need not be provided forthe respective systems, and one rotational angle sensor and onemicrocomputer may be provided in common for the two systems.

On the cover surface 238, the microcomputers 291, 292, capacitors 281,282, inductors 271, 272, and the like are mounted. In particular, thefirst microcomputer 291 and the second microcomputer 292 are disposed ata predetermined interval on the cover surface 238 that is the surface onthe same side of the same substrate 230. The capacitors 281, 282 smooththe power input from the power supply and prevent the outflow of noisecaused by the switching operations of the switching elements 241, 242,or the like. The inductors 271, 272 and the capacitors 281, 282correspond to L1, C1, and the like in each configuration diagram of theECU and constitute “noise prevention elements” that function as noisefilters.

As illustrated in FIG. 43, the three-phase motor 800 is a three-phasedouble winding rotating machine in which two three-phase winding sets801, 802 are coaxially provided. A voltage is applied from afirst-system inverter (hereinafter, “first inverter”) 601 to theU1-phase, V1-phase, and W1-phase windings 811, 812, 813 of the firstthree-phase winding set 801. A voltage is applied from a second-systeminverter (hereinafter, “second inverter”) 602 to the U2-phase, V2-phase,and W2-phase windings 821, 822, 823 of the second three-phase windingset 802.

The first three-phase winding set 801 and the second three-phase windingset 802 have the same electrical characteristics and are disposed on thecommon stator 840 so as to be offset from each other by an electricalangle of 30 [deg]. In this case, the counter-electromotive voltagesgenerated in the respective phases of each of the first system and thesecond system are expressed by, for example, Formulas (9.1) to (9.3) and(9.4a) to (9.6a) on the basis of a voltage amplitude A, a rotationalspeed ω, and a phase θ.

Eu1=−Aω sin θ  (9.1)

Ev1=−Aω sin(θ−120)   (9.2)

Ew1=−Aω sin(θ+120)   (9.3)

Eu2=−Aω sin(θ+30)   (9.4a)

Ev2=−Aω sin(θ−90)   (9.5a)

Ew2=−Aω sin(θ+150)   (9.6a)

When the phase relationship between the two systems is reversed, forexample, the phase (θ+30) of the U2 phase is (θ−30). Moreover, a phasedifference equivalent to 30 [deg] is generically expressed as (30±60×k)[deg] (k is an integer). Alternatively, the second system may bedisposed in the same phase as the first system. In this case, thecounter-electromotive voltages generated in the respective phases of thesecond system are expressed by Formulas (9.4b) to (9.6b) instead ofFormulas (9.4a) to (9.6a).

Eu2=−Aω sin(θ−30)   (9.4b)

Ev2=−Aω sin(θ+90)   (9.5b)

Ew2=−Aω sin(θ−150)   (9.6b)

Next, a configuration example of the ECU 10 that drives the two-systemthree-phase motor 800 will be described as the eleventh to fifteenthembodiments with reference to FIGS. 44 to 48. A portion where the firstthree-phase winding set 801 and the second three-phase winding set 802are combined is the three-phase motor 800. The reference character “800”of the three-phase motor and the reference characters “821, 822, 823” ofthe three-phase winding of the second three-phase winding set 802 areillustrated only in FIG. 44 and are not illustrated in FIGS. 45 to 48.The ECU 10 according to each of the eleventh to fifteenth embodimentsincludes two inverters 601, 602. The reference characters of theinverter switching element, the current sensor, the motor relay, and thelike of the second system are denoted by replacing “1” of the symbol ofthe first system with “2”. Regardless of the configuration of the powersupply, the DC voltage input to the second inverter 601 is referred toas an “input voltage Vr2”.

The reference characters of the DC motors connected to the U2 phase, theV2 phase, and the W2 phase of the second three-phase winding set 802 are“740”, “750”, and “760”, respectively, and the symbol of the operationvoltage at the neutral point is Vn2. Similarly to the DC motors 710,720, 730 of the first system, the counter-electromotive voltagesgenerated in the DC motors 740, 750, 760 of the second system arereferred to as E4, E5, E6, respectively.

The use of each of the DC motors 740, 750, 760 may be selectedappropriately. For example, any one of the DC motors 740, 750, 760 maybe a seat actuator or a steering wheel retraction actuator.Alternatively, steering actuators such as steering lock, tilt, andtelescopic actuators may be provided as the DC motors 740, 750, 760 onthe second system side.

The reference characters of the DC motor switches corresponding to theDC motors 740, 750, 760 are “MU4H/L, MV5H/L, and MW6H/L”, respectively.The reference characters of the DC motor relays corresponding to the DCmotors 740, 750, 760 are “MU4 r/R, MV5 r/R, and MW6 r/R”, respectively.The control unit 30 in the two-system configuration includes three-phasecontrol units of the first system and the second system based on FIG.15, and a DC control unit based on each of FIGS. 16A and 16B.

In the eleventh to fourteenth embodiments, the first inverter 601 andthe second inverter 602 are connected to a common power supply Bt1. Inthe eleventh to fourteenth embodiments, the total number anddistribution of the DC motors connected to the respective phases of eachof the first system and the second system are different. Thedistribution of the DC motors is determined in consideration of a powerbalance, a heat generation balance, a balance of a use frequency and ause timing, and the like between the systems.

Eleventh Embodiment

In the eleventh embodiment illustrated in FIG. 44, two DC motors 710,720 are connected to the U1 phase and the V1 phase of the firstthree-phase winding set 801. DC motor relays MU1 r/R, MV2 r/R areprovided between the branch points Ju, Jv of the U1-phase and V1-phasecurrent paths and the first terminals of the DC motors 710, 720,respectively. On the other hand, no DC motor is connected to the secondthree-phase winding set 802. In the eleventh embodiment, since the DCmotor is connected to only some of the plurality of systems, the rolesof the systems are shared.

Twelfth Embodiment

In the twelfth embodiment illustrated in FIG. 45, one DC motor 710 isconnected to the U1 phase of the first three-phase winding set 801, andone DC motor 740 is connected to the U2 phase of the second three-phasewinding set 802. With one DC motor being disposed in each system, thebalance between the systems is improved. Here, the DC motor relays MU1r/R in both positive and negative directions are connected to the DCmotor 710 of the first system, and only the DC motor relay MU4 r in thepositive direction is connected to the DC motor 740 of the secondsystem. For a protection function at the time of reverse connection ofthe power supply, it is possible to reduce the number of DC motor relaysby making at least one system redundant.

Thirteenth Embodiment

In the thirteenth embodiment illustrated in FIG. 46, the three DC motors710, 720, 730 are connected to the U1 phase, the V1 phase, and the W1phase of the first three-phase winding set 801, and one DC motor 740 isconnected to the U2 phase of the second three-phase winding set 802. Forexample, it is preferable to balance the power of each system bydisposing a DC motor of an actuator with relatively small power such asa steering-position actuator in the first system and disposing a DCmotor of an actuator with relatively large power such as a seat actuatorin the second system. However, the steering-position actuator and theseat actuator are rarely used simultaneously, and hence thesteering-position actuator and the seat actuator may be collectivelydisposed in the same system.

Fourteenth Embodiment

In the fourteenth embodiment illustrated in FIG. 47, the three DC motors710, 720, 730 are connected to the U1 phase, the V1 phase, and the W1phase of the first three-phase winding set 801, and the three DC motors740, 750, 760 are connected to the U2 phase, the V2 phase, and the W2phase of the second three-phase winding set 802. Here, the DC motorrelays MU1 r/R, MV2 r/R, MW3 r/R in both positive and negativedirections are connected to the DC motors 710, 720, 730 of the firstsystem, and no DC motor relay is connected to the DC motors 740, 750,760 of the second system. It is possible to reduce the number of DCmotor relays by making at least one system redundant.

Fifteenth Embodiment

The fifteenth embodiment illustrated in FIG. 48 is different from thefourteenth embodiment in the connection configuration of the powersupply. In the fifteenth embodiment, the first inverter 601 and thesecond inverter 602 are connected to a first power supply Bt1 and asecond power supply Bt2 separated from each other. The second inverter602 is connected to the positive electrode of the second power supplyBt2 via a high potential line BH2 and is connected to the negativeelectrode of the second power supply Bt2 via a low potential line BL2.Power supply relays P1 r/R, P2 r/R and capacitors C1, C2 areindividually provided in the input units of the respective inverters601, 602. In this manner, the fifteenth embodiment has a redundantconfiguration of so-called “complete two systems”.

The DC motor relays MU4 r/R, MV5 r/R, MW6 r/R in both positive andnegative directions are connected to the DC motors 740, 750, 760 of thesecond system. With this configuration, for example, when one powersupply fails, the three-phase motor 800 can be driven in a one-systemdrive mode using only the other power supply that is normal.

(Effects)

(1) The ECU 10 of the present embodiment (here, the reference charactersin the second embodiment and the like are used) can simultaneously drivethe DC motors 710, 720, 730 by controlling the operations of the DCmotor switches MU1H/L, MV2H/L, MW3H/L while controlling the operationsof the inverter switching elements IU1H/L, IV1H/L, IW1H/L to drive thethree-phase motor 800.

In the configuration where one DC motor 710 is connected to the phasecurrent path of one phase of one three-phase winding set 801 as in thefirst embodiment, it is sufficient that at least two DC motor switchesMU1H, MU1L be provided. Therefore, the number of switches can be reducedas compared to the conventional technique of JP5768999B2.

(2) The control unit 30 performs control to switch ON/OFF of the DCmotor switches on the high potential side and the low potential side inaccordance with the energization direction of the DC motor and toincrease or decrease the neutral point voltage Vn1 of the three-phasemotor 800. As a result, the control unit 30 can appropriately controlthe energization of the specific DC motor.

(3) In the ECU 10 of each embodiment except for the first embodiment, aplurality of DC motors are connected to a plurality of phases of onethree-phase winding set 801, or a plurality of DC motors in total areconnected to one or more phases of each of the plurality of three-phasewinding sets 801, 802. As a result, the ECU 10 can also serve as a drivefunction of a plurality of DC motor type actuators by a drive device forthe three-phase motor 800.

(4) The ECU 10 according to the present embodiment includes a pluralityof current sensors SAU1, SAV1, SAW1 that detect currents flowing throughthe respective phases of the inverter 601. The control unit 30 computesthe current flowing through the specific DC motor from the detectionvalues of the current sensors of the non-specific phase and the specificphase and the estimated current value of the specific phase on the basisof Kirchhoff's law. As a result, the control unit 30 can appropriatelycontrol the energization of the specific DC motor.

(5) The ECU 10 of the present embodiment is suitably applied, as thethree-phase motor 800, as a device that controls the drive of a steeringassist motor of the EPS system 901 or a reaction force motor of the SBWsystem 902. In this case, it is effective to use, as the DC motor, asteering-position actuator that makes the steering position variable,specifically, the tilt actuator 720 and the telescopic actuator 730.

Other Embodiments

(a) The DC motor terminal voltages Vm1, Vm2, Vm3 need not be adjusted toarbitrary values by the switching operation of the DC motor switchesMU1H/L, MV2H/L, MW3H/L by duty control or the like. It is sufficientthat at least the voltage value be made variable by switching betweenthe ON states of the switches MU1H, MV2H, MW3H on the high potentialside and the ON states of the switches MU1L, MV2L, MW3L on the lowpotential side. On the premise that the high-speed switching operationis not performed, a transistor or a mechanical relay that switchesslowly may be used. In addition, since there is a possibility that alarger current flows through the inverter switching element connected tothe DC motor than the other inverter switching elements, the inverterswitching element may have a capacity equal to or higher than those ofthe other switches or may be disposed in a place where heat generationis not concentrated or a place where heat radiation is better than thoseof the other switching elements.

(b) As the DC motor switches MU1H/L, MV2H/L, MW3H/L, switches havingcurrent capacities equal to or higher than those of the inverterswitching elements IU1H/L, IV1H/L, IW1H/L may be used. As the powersupply relay Pdr/R on the DC motor switch side, a switch having acurrent capacity equal to or higher than that of the power supply relayP1 r/R on the inverter side may be used. In addition, a dead time forpreventing each pair of the upper and lower switches from being turnedon simultaneously may be individually set in accordance with each switchand the magnitude of the flowing current, and the voltage forcompensating for the dead time may be individually set for each pair ofthe upper and lower switches in accordance with the set dead time andthe flowing current. The polarity determination of the compensationvoltage for the dead time is determined by the reference character ofthe current flowing through each pair of the upper and lower switches.

(c) For the DC motors 710, 720, 730 of the third embodiment and thelike, assuming a terminal ground fault, the negative-direction DC motorrelays MU1R, MV2R, MW3R need not be provided, and only thepositive-direction DC motor relays MU1 r, MV2 r, MW3 r may be provided.In addition, the direction of the series connection of thepositive-direction DC motor relays MU1 r, MV2 r, MW3 r and thenegative-direction DC motor relays MU1R, MV2R, MW3R may be a directionin which the drain terminals of the MOSFETs are adjacent to each other,contrary to FIG. 7 and the like.

(d) The three-phase motor relays MmU1, MmV1, MmW1 or the DC motor relaysMU1 r/R, MV2 r/R, MW3 r/R may be mechanical relays or bidirectionalrelays. When the three-phase motor relays MmU1, MmV1, MmW1 aremechanical relays or bidirectional relays, it is sufficient that thethree-phase motor relays MmU1, MmV1, MmW1 be provided in two phases. InFIG. 7, the source terminals of the three-phase motor relays MmU1, MmV1,MmW1 are oriented toward the inverter side, but the drain terminals ofthe three-phase motor relays MmU1, MmV1, MmW1 may be oriented toward theinverter side.

(e) The current sensor is not limited to a sensor that detects thecurrent flowing between the lower arm element of the inverter and thelow potential line BL1 but may directly detect the phase current.

(f) In the eleventh to fifteenth embodiments, the first system inverter601 and the positive-direction power supply relays, thenegative-direction power supply relays, and the noise preventionelements corresponding to the DC motor switches MU1H/L, MV2H/L, MW3H/Lare configured according to the third embodiment. On the other hand, theconfiguration of each system may be configured according to the fourthto eighth embodiments. The two systems may have the same configurationor different configurations.

(g) As illustrated in FIG. 49, the DC motor switch may be formed of adouble closure switch MU1DT. The double closure switch MU1DT can switchthe connection of the DC motor terminal M1 with a contact on the highpotential side and a contact on the low potential side.

(h) Each of the two DC motors is not limited to an independent form butmay be formed of a stepping motor having two-phase windings.

(i) The multiphase rotating machine is not limited to having threephases but may have two phases or have four or more phases, that is,generalized N phases (N is an integer of 2 or more). The multiphaserotating machine may include three or more multiphase winding sets.

(j) In the above embodiment, for the sake of convenience, the steeringlock actuator 710 also functions as the steering vibration actuator, butin practice, those actuators are generally achieved as separate motors.Therefore, one of the steering lock actuator and the steering vibrationactuator may be driven by another power converter.

(k) The rotating machine control device of the present disclosure is notlimited to a steering assist motor or a reaction force motor in asteering system of a vehicle, or a DC motor for a steering-positionactuator, a seat actuator, or the like, but can be applied as variousrotating machine control devices using a multiphase AC motor and a DCmotor in combination. The steering assist motor or the reaction forcemotor need not be an electromechanical integrated type but may be anelectromechanical type in which the motor body and the ECU are connectedby a harness.

The configuration of the present disclosure is more effective in avehicle motor in which various motors are disposed proximately, and isapplicable to combinations of, for example, a motor for a hydraulic pumpof a brake and a motor for a parking brake, a plurality of seat motors,a motor for a sliding door or a motor for a wiper, a motor for a windowand a motor for a side mirror, a motor for an electric water pump and amotor for an electric fan, and the like.

The present disclosure is not limited to such embodiments but can beimplemented in various forms without deviating from the spirit of thepresent disclosure.

The control unit and the technique according to the present disclosuremay be achieved by a dedicated computer provided by constituting aprocessor and a memory programmed to execute one or more functionsembodied by a computer program. The control unit and the techniqueaccording to the present disclosure may be achieved by a dedicatedcomputer provided by constituting a processor with one or more dedicatedhardware logic circuits. The control unit and the technique according tothe present disclosure may be achieved using one or more dedicatedcomputers formed of a combination of the processor and the memoryprogrammed to execute one or more functions and the processor includingone or more hardware logic circuits. The computer program may be storedin a computer-readable non-transitional tangible recording medium as aninstruction to be executed by the computer.

The present disclosure has been described in accordance with theembodiments. However, the present disclosure is not limited to theembodiments and structures. The present disclosure encompasses variousmodifications and modifications within an equivalent scope. Variouscombinations and forms, as well as other combinations and formsincluding only one element, more than that, or less than that, are alsowithin the scope and idea of the present disclosure.

What is claimed is:
 1. A rotating machine control device configured todrive one or more multiphase rotating machines including one or moremultiphase winding sets and one or more DC rotating machines in which afirst terminal that is one end is connected to a phase current path ofone or more phases of at least one of the multiphase winding sets, thedevice comprising: one or more multiphase power converters that areconnected to a positive electrode and a negative electrode of a powersupply via a high potential line and a low potential line, respectively,convert DC power of the power supply into multiphase alternate currentpower by operations of a plurality of inverter switching elementsconnected in a bridge configuration, and apply a voltage to each ofphase windings of the multiphase winding set; a DC rotating machineswitch made up of switches on a high potential side and a low potentialside connected in series via a DC motor terminal connected to a secondterminal that is an end of the DC rotating machine on an opposite sideto the first terminal, the DC rotating machine switch making a voltageof the DC motor terminal variable by switching; and a control unit thatcontrols operations of the inverter switching elements and the DCrotating machine switch, wherein at a time of energization in a positivedirection from the first terminal to the second terminal of the DCrotating machine, the control unit turns on the DC rotating machineswitch on the low potential side connected to the second terminal orcauses the DC rotating machine switches on the low potential side andthe high potential side connected to the second terminal to perform aswitching operation such that a voltage of the second terminal is lowerthan a voltage of the first terminal, and controls a neutral pointvoltage of the multiphase winding set to be higher, and at a time ofenergization in a negative direction from the second terminal to thefirst terminal of the DC rotating machine, the control unit turns on theDC rotating machine switch on the high potential side connected to thesecond terminal or causes the DC rotating machine switches on the lowpotential side and the high potential side connected to the secondterminal to perform the switching operation such that the voltage of thesecond terminal is higher than the voltage of the first terminal, andcontrols the neutral point voltage of the multiphase winding set to belower.
 2. The rotating machine control device according to claim 1,wherein the control unit adjusts the neutral point voltage in accordancewith a voltage that is applied to the multiphase winding set.
 3. Therotating machine control device according to claim 1, wherein thecontrol unit switches between drive and stop of the DC rotating machineby control of the neutral point voltage on a basis of a predeterminedcondition.
 4. A rotating machine control device configured to drive oneor more multiphase rotating machines including one or more multiphasewinding sets and one or more DC rotating machines in which a firstterminal that is one end is connected to a phase current path of one ormore phases of at least one of the multiphase winding sets, the devicecomprising: one or more multiphase power converters that are connectedto a positive electrode and a negative electrode of a power supply via ahigh potential line and a low potential line, respectively, convert DCpower of the power supply into multiphase alternate current power byoperations of a plurality of inverter switching elements connected in abridge configuration, and apply a voltage to each of phase windings ofthe multiphase winding set; a DC rotating machine switch made up ofswitches on a high potential side and a low potential side connected inseries via a DC motor terminal connected to a second terminal that is anend of the DC rotating machine on an opposite side to the firstterminal, the DC rotating machine switch making a voltage of the DCmotor terminal variable by switching; a control unit that controlsoperations of the inverter switching elements and the DC rotatingmachine switch; and a plurality of current sensors that detect currentsflowing through the respective phases of the multiphase power converter,wherein when one of the one or more DC rotating machines selected as anenergization target is defined as a specific DC rotating machine, andwhen a phase to which the specific DC rotating machine is connected isdefined as a specific phase, and a phase except for the specific phaseis defined as a non-specific phase, at a time of energization of thespecific DC rotating machine, the control unit computes, as an estimatedcurrent value, a value of a current flowing through the specific phasefrom a value of a current detected by the current sensor of thenon-specific phase according to Kirchhoff's law, and computes a currentflowing through the specific DC rotating machine from the estimatedcurrent value and a value of a current detected by the current sensor ofthe specific phase.
 5. The rotating machine control device according toclaim 4, wherein the current sensor is installed between a switchingelement on the low potential side of each of phases of the multiphasepower converter and the low potential line.
 6. A rotating machinecontrol device configured to drive one or more multiphase rotatingmachines including one or more multiphase winding sets and one or moreDC rotating machines in which a first terminal that is one end isconnected to a phase current path of one or more phases of at least oneof the multiphase winding sets, the device comprising: one or moremultiphase power converters that are connected to a positive electrodeand a negative electrode of a power supply via a high potential line anda low potential line, respectively, convert DC power of the power supplyinto multiphase alternate current power by operations of a plurality ofinverter switching elements connected in a bridge configuration, andapply a voltage to each of phase windings of the multiphase winding set;a DC rotating machine switch made up of switches on a high potentialside and a low potential side connected in series via a DC motorterminal connected to a second terminal that is an end of the DCrotating machine on an opposite side to the first terminal, the DCrotating machine switch making a voltage of the DC motor terminalvariable by switching; and a control unit that controls operations ofthe inverter switching elements and the DC rotating machine switch,wherein the control unit performs abnormality detection of themultiphase power converter or the multiphase rotating machine andswitches a fail-safe threshold in the abnormality detection between adrive time and a non-drive time of the DC rotating machine.
 7. Therotating machine control device according to claim 1, wherein aplurality of the DC rotating machines are provided, and a plurality ofthe DC rotating machines are connected to a plurality of phases of oneof the multiphase winding sets, or a plurality of the DC rotatingmachines in total are connected to one or more phases of each of aplurality of sets of the multiphase winding sets.
 8. The rotatingmachine control device according to claim 1, wherein a DC rotatingmachine relay is provided closer to the DC rotating machine than abranch point to the DC rotating machine in a phase current path from themultiphase power converter to the multiphase rotating machine.
 9. Therotating machine control device according to claim 1, wherein amultiphase rotating machine relay is provided in each of one or morephases between the multiphase power converter and the multiphase windingset, and in the phase to which the DC rotating machine is connected, themultiphase rotating machine relay is provided closer to the multiphaserotating machine than the branch point to the DC rotating machine in aphase current path from the multiphase power converter to the multiphaserotating machine.
 10. The rotating machine control device according toclaim 1, wherein the multiphase power converter and the DC rotatingmachine switch are connected to individual power supplies.
 11. Therotating machine control device according to claim 1, wherein the DCrotating machine switch has a smaller current capacity than a currentcapacity of the inverter switching element.
 12. The rotating machinecontrol device according to claim 1, wherein a power supply relay in anegative direction that is capable of interrupting energization from thepower supply when an electrode of the power supply is connected in adirection opposite to a normal direction is provided in common to themultiphase power converter and the DC rotating machine switch.
 13. Therotating machine control device according to claim 12, wherein a powersupply relay in a positive direction that is capable of interruptingenergization from the power supply when the electrode of the powersupply is connected in the normal direction is further provided incommon to the multiphase power converter and the DC rotating machineswitch.
 14. The rotating machine control device according to claim 1,wherein a power supply relay capable of interrupting energization fromthe power supply is individually provided for the multiphase powerconverter and the DC rotating machine switch, and the power supply relayon the DC rotating machine switch side has a smaller current capacitythan a current capacity of the power supply relay on the multiphasepower converter side.
 15. The rotating machine control device accordingto claim 1, wherein a noise prevention element functioning as a noisefilter is provided in common for the multiphase power converter and theDC rotating machine switch.
 16. The rotating machine control deviceaccording to claim 1, wherein a noise prevention element functioning asa noise filter is individually provided for the multiphase powerconverter and the DC rotating machine switch.
 17. The rotating machinecontrol device according to claim 1, wherein the multiphase rotatingmachine is a three-phase double winding rotating machine in which twothree-phase winding sets are provided coaxially.
 18. The rotatingmachine control device according to claim 17, wherein a same number ofthe DC rotating machines are connected to each of the two three-phasewinding sets.
 19. The rotating machine control device according to claim17, wherein different numbers of the DC rotating machines are connectedto the two three-phase winding sets, or the DC rotating machine isconnected to only one of the three-phase winding sets.
 20. The rotatingmachine control device according to claim 17, wherein the multiphasepower converters or the DC rotating machine switches are provided in twosystems.
 21. The rotating machine control device according to claim 1,further comprising: a plurality of the multiphase power convertersconnected to individual power supplies.
 22. The rotating machine controldevice according to claim 1, wherein in a case of energization of the DCrotating machine and non-energization of the multiphase rotatingmachine, the control unit turns on the inverter switching element on thehigh potential side and turns off the inverter switching element on thelow potential side of the phase to which the DC rotating machine to beenergized is connected, and the control unit turns off the DC rotatingmachine switch on the high potential side and turns on the DC rotatingmachine switch on the low potential side, or causes the DC rotatingmachine switches on the low potential side and the high potential sideconnected to the second terminal to perform a switching operation suchthat the voltage of the second terminal is lower than the voltage of thefirst terminal, or the control unit turns off the inverter switchingelement on the high potential side and turns on the inverter switchingelement on the low potential side of the phase to which the DC rotatingmachine to be energized is connected, and the control unit turns on theDC rotating machine switch on the high potential side and turns off theDC rotating machine switch on the low potential side, or causes the DCrotating machine switches on the low potential side and the highpotential side connected to the second terminal to perform the switchingoperation such that the voltage of the second terminal is higher thanthe voltage of the first terminal, or the control unit causes theinverter switching element of each of the phases to which the DCrotating machine to be energized is connected to perform the switchingoperation such that terminal voltage of each of the phases becomes asame voltage, and at a time of energization in the positive directionfrom the first terminal to the second terminal of the DC rotatingmachine, the control unit turns on the DC rotating machine switch on thelow potential side connected to the second terminal or causes the DCrotating machine switches on the low potential side and the highpotential side connected to the second terminal to perform the switchingoperation such that the voltage of the second terminal is lower than thevoltage of the first terminal, and at a time of energization in thenegative direction from the second terminal to the first terminal of theDC rotating machine, the control unit turns on the DC rotating machineswitch on the high potential side connected to the second terminal orcauses the DC rotating machine switches on the low potential side andthe high potential side connected to the second terminal to perform theswitching operation such that the voltage of the second terminal ishigher than the voltage of the first terminal.
 23. The rotating machinecontrol device according to claim 1, wherein the multiphase rotatingmachine is a rotating machine for steering assist torque output of anelectric power steering system or for reaction torque output of asteer-by-wire system.
 24. The rotating machine control device accordingto claim 23, wherein the DC rotating machine includes asteering-position actuator that makes a steering position variable.